Airframe failure: not just V-tails

All hell broke loose… then, only wind noise

A recent accident involving a vacuum failure in a V35B Bonanza and subsequent loss of control and airframe failure made me recall that this was a really substantial problem in the 1980s and early 90s. It also made me recall one of the better private flying war stories – from a pilot who survived an airframe failure.

This pilot was testing a Piper Seneca for a company that was seeking approval for airframe modifications on that aircraft. The flight on the day in question was to check flutter margins. (To appreciate the importance of flutter, watch this video before continuing to read. Plum scary.)

As I understood it, the proper procedure was to increase airspeed in small increments and pulse the elevator control after each increase. As the airplane came close to the flutter limit, an airframe anomaly would develop, more often than not in the horizontal tail, telling the pilot that was enough already. This would be done at speeds in excess of Vne, thus the term flutter margins. The faster an airplane is flying, the more susceptible it is to flutter. The margin would be the difference between the never exceed speed and the speed at which flutter started.

This pilot anticipated no problems and was in a hurry so he was increasing the airspeed in larger increments than recommended before pulsing the wheel.

That was when everything came unglued. He related incredibly loud noises as the airframe disassembled itself. Extremely high g-forces were also felt before serenity returned and only wind noise remained. The pilot had a good four-point restraint system and a crash helmet and was unscathed by the airframe breakup violence that probably lasted only a few seconds.

The pilot also had a parachute firmly strapped on and, when reality set in, he exited what was left of the airplane, popped his chute, and descended to a mountainside.

They knew right where he was and sent a helicopter, a really minimalist helicopter. When the Brantly B-2 came into view, the pilot wondered if the little two-seater would be up to the task. It was, the happy ending followed, and he was telling me the story a few weeks later.

People have survived airframe failures in flight without the help of a parachute. I actually remember one case, but just one, in the over 50 years I have been reading accident reports. In other words, if the airframe fails, the rest of the day doesn’t look good.

V35 crash
In-flight breakups almost never end well.

The Bonanza that was lost recently was being flown by a 4,000 hour ATP. The pilot reported a vacuum system failure and added that he was VFR on top and would continue to his destination. Then the airplane flew back into IMC and the pilot reported losing control of the airplane. It broke up shortly after that.

The debris path of the airplane was less than half a mile long. The right ruddervator was at the beginning of the debris path followed shortly by other wing, tail and fuselage parts. The engine and instrument panel were at the end of the debris path.

The NTSB is descriptive in outlining the debris path in such accidents for good reason. Any airframe will fail if operated far enough outside the envelope and it’s useful to know what fails first. You haven’t been tuned in over the years if you didn’t know that it’s the V-tail on a Model 35 Bonanza. The tails were required to be strengthened a while back but from that most recent event, it looks like the tail still fails first.

Accidents like this used to be commonplace, so much so that the NTSB/FAA went through three periods of near-panic on the subject. One was caused by vacuum pump failures.

The first accident posted in an NTSB safety recommendation came in early-1982. It was the in-flight breakup of a Cessna P210 following a vacuum system failure in IMC. The reason this accident made the subject pop to the surface was the fact that four prominent professional people were lost in the accident.

A Cessna T210 was listed next. There were two instrument-rated pilots in the aircraft and they made it through 20 minutes of partial panel flying after the vacuum failure only to lose control on an attempted ILS approach.

In another Cessna T210 accident the pilot was flying at Flight Level 190, above the clouds, when he was cleared to 13,000 feet. The pilot lost control of the airplane shortly after entering the clouds and the aircraft broke up in flight. The vacuum pump had failed.

A Mooney M20F with four on board was flying above clouds when the pilot reported a vacuum failure. The pilot continued on toward his destination and was subsequently cleared to descend into the clouds. Shortly thereafter the airplane crashed in a steep, high speed, nose down attitude.

Vacuum pump
The temperamental vacuum pump has caused a number of fatal crashes over the years.

Still another Cessna T210 was lost after the pilot reported a vacuum failure while flying at 12,000 feet, above the clouds. He was cleared direct to a requested airport and given a lower altitude. Shortly after entering the clouds at about 10,000 feet the pilot lost control of the aircraft. The right wing and empennage separated in flight. Four lost. (FYI, after this Cessna tested a 210 wing to destruction. It reportedly failed at above 7-g which is well in excess of the 5.7-g ultimate load factor requirement for this airplane.)

These accidents happened in about one year.

The NTSB took aim at vacuum systems, especially on Cessna 210s with deicing equipment. Because I had one, I did test flying in connection with this and you can read about that in my post about my experiences with the P210 and what was done to improve the reliability of the vacuum pump used on that airplane.

The NTSB came up with a laundry list of recommendations for the FAA to address this problem. I’ll sum them up.

An Emergency AD requiring dual vacuum pumps on Cessna 210s with deicer boots was called for plus a design certification review of the pneumatic portion of the deicing system on that airplane.

There were extensive other recommendations related to engineering evaluations of vacuum systems as well a new requirements for certification of airplanes with boots as well as some new requirements for turbocharged airplanes.

There were also recommendations for more rigorous pilot training and recent experience requirements on partial panel operations.

As is usually the case, the FAA followed some of the NTSB recommendations and pretty much ignored others.

Things settled down for a while but up jumped the devil in the late 1980s. This time vacuum pumps were not the culprit and only one type was involved. From May 31, 1989, to March 17, 1991, Piper PA-46 (Malibu or Mirage) airplanes were involved in seven airframe failure accidents worldwide. Five happened in the U.S., one in Japan and one in Mexico.

This activity got the undivided attention of the NTSB and the FAA. The NTSB did a special investigative report (NTSB/SIR-92-03) on the subject and the FAA did a special certification review on the PA-46 which is, in effect, a complete review of the certification of the airplane.

First, the wrecks. Because more complete information was available on those that happened in the U.S. the NTSB report concentrated on those.

In every case, the pilot lost control and the airframe failed. The vacuum system was not implicated in any of the accidents. One originated in a thunderstorm. That happens in all types so the airframe failure was all that accident had in common with the other four.

NTSB graph
The NTSB found that airframe failures lead to sudden and catastrophic endings.

The NTSB detailed the debris pattern and in most failures it appears that the horizontal tail failed first. A possible exception was one where control was lost at high altitude, the pilot had the foresight to extend the landing gear to limit the speed buildup, and the airplane emerged from the clouds at 2,000 feet, apparently in one piece. Despite the gear being down the speed was still high. The nose was down 15 to 20 degrees and when the pilot saw the ground he apparently pulled too hard to get the nose up. A witness said that both wings broke off simultaneously.

In the special certification review the FAA obviously looked at the airplanes’ ability to withstand the required 5.8-g ultimate loads. As Cessna had previously done, Piper went beyond that to see what loading would eventually cause the wings to fail. The result was about the same as for the Cessna 210: 7.7-g.

No smoking gun could be found in or about the PA-46 so they turned to the pilots and, guess what, they identified the culprit. A common thread was that ice was likely and the pitot heat had not been activated by the pilot. There was also a strong suggestion that the autopilot had not been operated in a proper manner. These items led to a review of the training programs for the airplane.

There was one incident (as opposed to accident) in the report and it is of special interest because the pilot lived to tell the story. This well illustrates how there can be a great difference between what a disoriented pilot thinks is going on and what is actually going on.

The Malibu was flying normally and level at FL180 when the pilot noticed some cumulus buildups ahead and requested a higher altitude. The controller cleared the flight to FL200.

The pilot programmed the autopilot for the climb and as soon as it was engaged in the climb mode the airplane pitched up sharply to a much more nose-up attitude than the pilot expected. He disengaged the autopilot as the airspeed reached zero. The pilot reported that the airplane then stalled. He also remembered observing the manual trim wheel complete a move to the full nose-up position.

The pilot said he attempted to push forward on the controls but that the airplane entered a left spin or spiral into the clouds. The pilot said that the uncontrolled descent in a spin or spiral continued until he was able to recover when the airplane exited the clouds at 3,000 feet. The pilot said he might have recovered near 7,000 feet but the airplane resumed the spin or spiral.

The pilot was talking to the controller the whole time and there was apparent confusion. Once he was in VFR conditions he first said he was in visual conditions but the airplane would not respond to any power setting. Then the pilot said he was at 3,000 feet, flying level.

The NTSB reconstructed the flightpath and once the airplane departed from controlled flight at FL180 it showed wide speed variations, to a groundspeed as high as 250 knots (Vne is 203 knots). The descent slowed briefly at 14,000 feet but then continued rapidly to 9,000 feet after which the airplane climbed back to 11,600 feet.

For the next five minutes the airplane flew through a series of climbs and descents and sharp turns left and right. Then the pilot reported level at 3,000 feet.

At some point in the proceedings, an airline pilot suggested that the Malibu pilot turn the pitot heat on. The NTSB speculated that this was probably sufficient to alert the pilot that his airspeed indication was erroneous.

The pilot estimated he had about 650 hours which included 20 hours of instrument flight time, about five or six of which was in actual instrument conditions. The pilot had attended the Piper school on the PA-46 and had flown the airplane for about 70 hours.

After the pilot landed, numerous loosened rivets were found in the aircraft structure, the elevator trim tab was bent and the right wheel well door was missing. Nobody knows how close the airframe was to failing but it was probably at least nibbling at the edges.

As has been often true, the event began with a low-speed loss of control which evolved into a spiral dive (graveyard spiral) that results in speed well in excess of Vne.

Avidyne autopilot
If you don’t know how to use the autopilot, it can quickly get you into a stall.

In the investigation of the factory training program for the PA-46 it was found that it provided minimal instruction on the use of the KFC 150 flight control system especially including the vertical speed and altitude selection features.

In the training the student’s instrument flying skills were evaluated to some extent and instructors made recommendations on whether further training was needed. There was no training on recovery from unusual attitudes in IMC or on partial panel instrument flying.

In the heat of battle the FAA issues the obligatory airworthiness directive on the P-46. As you might imagine, it was a touch Draconian.

Flight in instrument meteorological conditions was prohibited.

Use of the autopilot or associated devices for altitude changes was prohibited and to back this up it was required that the control panel for these functions be removed from the aircraft.

It was required that the pitot heat and alternate induction air be on at all times except during takeoff and landing.

It was recommended that flight into area of known or forecast moderate or severe turbulence be avoided.

Within a month the FAA lifted the prohibition on flight in IMC and added that flight into known or forecast ice, thunderstorms, moderate or severe turbulence was prohibited. Virtually all PA-46 airplanes were equipped and approved for flight in icing conditions; this effectively removed that approval.

About ten months later, the FAA rescinded the AD.

One thing the NTSB recommended but that was rejected by the FAA related to the requirement for special training before operating a pressurized airplane certified for flight above 25,000 feet. The NTSB wanted the altitude lowered to 18,000 feet, to include the PA-46 and P210 airplanes and if the FAA had put any thought into this that would have been done. There must have been a strong lobby against the change.

The V-tail Bonanza has also undergone a special certification review prompted by a number of airframe failures in that type over a lot of years. (The V-tail started coming to the fleet as a 1947 model.) One thing that might have added to interest in this was the fact that the Model 33 Bonanza (originally the Debonair) didn’t have a history of airframe failures and the primary difference between the two airframes is the tail.

Every airplane has some flying surface that will let go first and on the V-tail it was indeed found to be the tail.

V-tail Bonanza
The most thoroughly tested airplane in the private aviation fleet?

Under some combination of high speed, turbulence induced air loads, and pilot control input the twisting loads that developed on the tail could lead to a failure. The ground and flight tests that revealed this were more thorough than those found in normal certification work and it might be said that the V-tail Bonanza airframe is the most thoroughly tested in the private aviation fleet.

There were ADs, mainly restricting the speed at which V-tails could be flown. There were fixes to restore the original limitations and this action did confirm that under extreme circumstances the airplane might not have met the certification standards even though the FAA and Beech had held that it did.

Ironically, in more than half of the approximately 230 V-tail airframe failures that occurred up to the late 1980s, the wings failed first. If the number of failures seems high, over 10,000 V-tail Bonanzas were built and were flown in this 40-year period

Even though the Mirage and V-tail were the airplanes where the structure was questioned, the airframe failure rate in those types is about the same as in the Cessna 210s and Piper PA-32 retractables. The simple truth is that if you lose control and the speed and/or g-loading goes outside the envelope some part of the airframe will likely fail, leading to the failure of other parts.

If this type accident is declining, and it does appear to be doing so, there are two main reasons this might be so. Training has become many times better in the past 30 years and more pilots now have a better understanding of autopilots and airplane limitations. The other reason is a negative. There is simply far less flying being done and pilots pushing weather to get utility out of these airplanes is being done far less often. Certainly the airplanes have not grown stronger and the weather has not become more forgiving.

In closing, a technique note. We all know that reducing the angle of attack will greatly lessen the likelihood of a low speed loss of control. The solution to avoiding a high speed event is just as simple. If things are going crazy, just keep the wings level. This can be done with the most basic instrument (turn and bank or turn coordinator) or with attitude indication. Some autopilots have a panic button that will do this for you. If you ever let a cat out of a bag and tried to put it back in, you know how much easier it is to just keep the cat in the bag.

37 Comments

  • These days a simple back up to your expensive vacuum pump comes in the form of a 0.99cents app on your phone.

    The iPhone 6 and 6 plus have such precise accelerometers that it can easily give you an emergency AI when everything goes Tango Uniform. I use the one called Gyro.

    • Yep. Everyone should fly with a current iPhone or iPad and practice using it as a panel replacement from time to time. This way if the real thing happens, you’ll be familiar with the setup. There are great utilities available and the solid-state accelerometer is indeed hyper-accurate.

    • Liad – I am all for taking advantage of cheap readily available electronic redundancy with current smart phones and tablet computers. The drawback to a hand held accelerometer device is that, unless you use a sensor that is firmly mounted to the airframe and calibrated such as those used in combination with several of the ADS-B in receivers being sold today, the attitude indication is pretty crude and “shaky” and not all that useful except as a dire emergency backup.

      The reality is, the probability of losing both the vac pump and electric system at the same time, or losing both the vac-powered attitude indicator and the electric powered turn coordinator at precisely the same time, is quite low.

      All pilots should train themselves to include the turn coordinator in their regular instrument panel scan at all times, so that it is natural to switch their scan to the TC in the event the AI goes TU. It’s very easy to make that change if it’s already part of your eyeball memory. It will be precise, unlike a smart phone accelerometer held in a shaky hand or mounted to the yolk which, of course, rotates whenever you maneuver the aircraft. The failure rate of electric TCs is far below that of the unreliable vac systems … and of course, you have a “battery backup” even if the alternator fails in flight.

      A better solution than hand held smart phone “panels” is dedicated backup instruments that are powered off the aircraft electrical bus and have built-in batteries for when the aircraft electrical system goes down. With the FAA’s recent decision this year to approve a low cost system formerly restricted to experimental aircraft for use on certified aircraft, we now have the option to provide a great backup panel at fairly low cost (more than 99 cents, though 🙂 )

  • I knew the Seneca test pilot you speak of. There was a cockpit mounted camera on that test flight and I have seen the film. What impressed me was that there was no warning from the previous test condition and no warning on the final condition. He just pulsed the control wheel and the camera came flying out of the mounts. Flutter is serious stuff indeed.

  • Great article. I’ve heard Beech V-tail stories almost all my life, starting in late 50s I believe, which bothered me since I loved the looks of the plane. In the 70s I bought a V-tail competition sailplane and, as a lot of guys said, if you didn’t look back, you wouldn’t know what type of tail it had by its flying.

    • BTW, competition sailplane pilots fly with a chute, no matter the type of tail. Competition can get a pilot extremely close to aircraft limits and so does going after records or badges.

  • This is a question for Dick rather than a comment:

    Why – in your opinion do so many instrument rated pilots lose aircraft control with the loss of the vac pump (and the vacuum-powered attitude indicator), when it is so easy to just use the turn coordinator to keep the wings level (as you suggest at the end of your post)?

    To me, it has always seemed intuitive to look at the turn coordinator as part of my panel scan even in VFR conditions. I almost always glance at it at least momentarily when I bank the aircraft more than a few degrees. Yet apparently quite a few instrument pilots fail to use the obvious backup instrument to keep wings level. Gaging the deck angle is also easily accomplished with a combination of airspeed, VSI, and altimeter.

    I get that flying partial panel is a bit more of a challenge than full panel when one is in the soup. Yet I don’t get why so many instrument rated and supposedly current pilots seem to be unable to do so at all. Does a part of the pilot’s brain simply tend to go blank when confronted with a partial panel?

    • Well Duane, I’m not Dick, but I have an answer for you.

      In training, the instructor covers the gyro instruments and says, “OK, you’re partial-panel”. You know exactly what has happened, and you respond accordingly.

      In the real world, the gyros fail slowly, and you follow what they are saying until you realize (through your cross-check) that something isn’t right. Unfortunately, many times the pilot does not detect the problem until he is already in trouble. The pilot got into trouble because he wasn’t keeping up his cross-check (due to inadequate practice) and did not respond to the unusual attitude correctly (due to inadequate practice).

      Like Dick said, it’s easier to keep the cat in the bag (always be cross-checking) than to put it back in (sudden and unexpected need for a partial-panel unusual attitude recovery).

      Current or not, I go out and practice partial-panel unusual attitude recoveries every 6 months. I grab a pilot friend, do some hood-work, then buy lunch as a thank you.

      • Ed’s reply is right on. I would add that any time a pilot faces something he perceives as unusual there could be problems. I have always thought we should put more emphasis on partial panel flying so pilots won’t see it as unusual when and if the time comes.

        • Ed & Dick,

          Thanks for your replies. I understand your explanation. Personally, having suffered two vac failures, I learned pretty early on to not rely on the AI to fly the airplane.

          Speaking of that, it’s become cliche in recent years for folks who dislike or have low regard for glass panel instrumentation to denigrate those who do like the new stuff as “magenta line pilots”, as if such pilots are not capable of doing anything but flying the magenta line on the glass.

          Well, apparently there was and is a steam gage equivalent … those are the “AI pilots”, those who only seem to know how to fly the little airplane device on their AI. It is stating the obvious that all pilots should fly the whole airplane, not just using one individual source of information, while ignoring the rest of the airplane and the instruments.

        • There is a simple pilot awareness that has been overlooked by the aviation safety community. The NTSB and the FAA agree with my analysis, but their bureaucracies have been unable to deal with it. I have letters and e-mails from both. Also e-mails from Boeings chief pilot, and the head of American Airlines Flight Academy. They all agree that this simple awareness would have prevented the crash of AF447, and reading through your various articles on crises caused by loss of vacuum, would be of great help in those situations too. I would like to talk to Richard Collins about this situation. You have my e-mail address and my phone # is 336-355-9123.

        • Good Evening Richard,

          Just rereading this article about the V-tail when I noted that the beautiful airplane shown is none other than my 1978 V35B N20318 which we have had since late 1989.. The photo was taken by my daughter in law who was riding in the right seat of a model 33 flown by her husband, our oldest son. Small world is it not?

          Happy Skies,

          Old Bob

  • Airframe failure is one of the more terrifying ways an airplane can kill you, because you’ll have what seems like a long time as you fall to the ground to realize you’re done for, but can’t do anything about it. I had an experience that seemed to me like an airframe failure at the time, but luckily, it wasn’t. Cruising at 6,000 feet in a Bonanza f33 on an IFR flight plan but VMC, approaching JFK VOR from the east, I encountered some turbulence that triggered a loud bang, followed by a whooshing sound of air flow. I was terrified, absolutely convinced I’d had an airframe failure and my lifetime could be measured in minutes.
    I must have sat frozen at the controls for two whole minutes. At that point I realized the airplane was still charging ahead at 155 knots, barely off the heading and altitude I’d been assigned. Could it be something else? Maybe just a failure in the ventilation system that made the noise? I tried to troubleshoot that and found nothing. Open baggage door? Nope. I climbed 50 feet and then descended 50 feet very gently. Normal behavior from the bird. What the **** could it be?
    At this point New York Approach called, rather testy, asking if I would favor them with a turn to the south now since I’d already overflown the field. gulp! Well, I was aviating, and that takes precedence over navigating and communicating. I looked at the VOR gauge and it was showing station passage, pegged to the left, so the field was off my left quarter. I turned around to see it and found — OMG!!! The left rear WINDOW had popped open!!! Well of course it made a whooshing sound….I turned rather smartly onto my new heading and all was well. Except that the manual says the F33A is not approved for flight with side windows open. Ha ha.

  • The BE 35, V-tail and the BE33 straight tail share a CG trait, the only station located forward of the forward CG limit is fuel. Fuel is ballast. When loaded heavy, pilots reduce fuel to stay under gross T.O. weight.
    But many pilots fail to do a zero fuel W&B or determine the minimum ballast fuel required for landing. If you fly any airplane with the CG on the aft limit, you will find that the ailerons may still be heavy but the up pitch control becomes very light, one finger is all that is needed to change pitch. Over control becomes very likely. When aft of the limit, the plane might still be controllable, but it becomes even easier to pull 10 Gs.
    Part 23 set control forces so pilots can fly without serious risk of over stressing the airframe. But mix CG, turbulence, maybe some control friction because the cables and pulleys haven’t been lubricated recently, and pilots can easily break the airplane.
    Va & Vb reduce with weight, CG shifts with fuel burn and too many pilots fail to understand W&B and failure modes of autopilts and flight instruments.

    • A “ballast” event happened to me as I was climbing out of South Lake Tahoe in a grossed out Cessna. A friend had brought his bowling ball on our weekend tip to the lake. On take-off (pressure altitude 10,000 ft.) the ball decided to roll back in the luggage compartment, putting the CG out of the envelope.
      This all occurs just about 100 meters over the trees on departure. The lesson; secure your bowling balls – Flying, everyday, a new lesson.

  • No special comment other than on the Beautiful photo you used in the article showing my 1968 V35B N20318 S/N D-10173. It was taken by our daughter in law flying with our oldest son, Bob II, in his 1965 S35 N8939U. I have had the V35B since 1989 and owned many Bonanzas before that one. Been flying Bonanzas regularly since 1952.

    For what it is worth, my first two had no artificial horizon. Those were not required before 1955. I was trained using needle, ball, and airspeed. Worked great. It is my feeling that the worst thing that ever append to aviation was the Turn Coordinator replacing the T&B. Since that happened, no one has any skill with partial panel. Pity.

    Thanks for showing the picture of my valiant steed!

    Happy Skies,
    Old Bob

  • When I first learned to fly (1955), the turn coordinator was the BASIC instrument in this mix. The HSI, while it provides a more easily evaluated and clearly presented picture, was taught as a SUPPORT instrument. It seems that many of today’s GA pilots are more than a little uncomfortable with true primary panel instrument flight. My thought is that today’s CFIs might pay a bit more attention to real primary panel aircraft control.

    Forgive this ol’ mossback if I’m out of line here . . .

    • Hi Mort, Another addition if I may. When you learned to fly, the Turn Coordinator had not yet been invented. It started to appear in the early sixties and was generally used as the stabilizing source for low cost autopilots. Worked well for that purpose. My opinion, (which does not seem to be worth much these days), is that the Turn Needle is what we need. The TC shows a roll or a turn. Seems like a good idea, does it not? Unfortunately, that can add to the confusion. Have you ever flown a knife edge? The TC will tell you the wings are level. The T&B always tells the truth. If it is centered, you are not turning. Period! I have always taught my students to include the T&B in their scan so as to know what their rate of turn really is. I do not care what that rate is, but including it in normal scan will help pick up a failure of the attitude indicator. If we do not include the TC or T&B in our normal scan, we are unlikely to note the change in time to correct the situation. There is nothing on the panel that looks anything like a T&B. Center the needle and you will survive. No need to try to figure out which way is up. Just center the needle and you WILL survive. Who cares which way is up!!

      Happy Skies,

      Very Old Bob

      • Hey, Old Bob,

        You’re right, of course. I didn’t ream the “turn coordinator,” I meant the turn-and-bank. The T&B was our primary attitude instrument. With the airspeed instrument and the altimeter, you and I had all we needed to fly ——– safely and confidently.

        • When I took my SEL check ride in my own Cessna 140A in the mid ’70s, all I had was a T&B, airspeed and altimeter and it took me some time to find a check pilot who would/could do my check in a tail dragger with these instruments. He was in a big city 90 miles from my base.

          That check ride almost resulted in me quitting flying when the check pilot nearly killed us when I was landing in a strong crosswind and the older pilot took over the controls in my wheel landing and pulled the tail down while we were still carrying a lot of speed.

          In fact, it also took me a long time to find a flight instructor. Fortunately, I lived in a smallish town and found a young crop duster/180 pilot in a nearby small town with a CFI ticket.

      • Bob,

        The old T&B is better as a primary turn-monitoring device once an aircraft has entered an unusual attitude, for the reasons you wrote. But it’s always better to keep an active cross check and avoid entering the unusual attitude in the first place.

        Unfortunately there aren’t many of those old “dog house” instruments left these days. I’ve been flying 40 years and have never had one in my panel. No point in crying over spilt milk as the old timers use to say.

        Today, however, there are multiple practical solutions readily available.

        From all electric AIs that are much more reliable than vac driven AIs (which are virtually guaranteed to fail every few hundred hours); to all electronic AHRSs and ADCs that fail far less often than electric AIs; to fully independent panel mount electronic AI/TC/ADC combos with backup batteries; to fully independent portable AHRSs that are now packaged with portable ADS-B in receivers; to portable pad computers and smart phones with built in accelerometers and cheap apps.

        Not to mention that the rate-based autopilots, working off the reliable TC instrument, can keep one from entering an unusual attitude when flying in the soup. Prevention being much better than having to find a cure in the air.

        So in today’s world, with a range of relatively cheap backup systems readily available, there is no good excuse for a pilot to not have ample redundancy in attitude instrumentation at hand that will allow the pilot to always keep it sunny side up. We won’t be turning the clock back to the 1950s … at the same time, we pilots really do owe it to ourselves and our passengers to enter the 21st century.

        Respectfully,

        Duane

  • When someone asks me to advise them regarding fast singles or twins they want to use for getting there fast and in all weather conditions,my answer is typical.
    A fast AC will not be as fast as we think or as safe as it was designed if the pilot is not well trained / educated / experienced in a variety of aviation related subjects.
    -The ” salesman” wants money, the more the better.
    – I want you to be safe and educated before you decide to buy a fast machine.
    Then I mention this simple observation I made in one of my routine training flights in KTPA area when the airspace was designated ARSA.
    A Bonanza pilot was transitioning through the “Bay Area” southbound to KMIA, he was very actively speaking to the busy controllers telling them that he was from the ” real Bay Area” (LA). He asked for a GS reading and he received a prompt answer, then he wanted everyone to know how how “smart of an Alec” he was and out of the blue said to the ATC: You guys talk funny around here.
    The controller was polite but soon I heard him give the Bonanza a heading that was very much like a course designed to take him to Mexico.
    The reason, avoiding numerous F-16 traffic from the nearby training base.
    Needless to say, the slow taildragger bellow at 1100 feet made a smooth transition over the Sunshine Skyway Bridge and was well ahead South while the fast single was doing 360s over the Gulf.
    We are as fast and safe as we can manage to be.
    Get as much experience on a slow low budget AC and be courteous to the controls and the controllers, then you can get there ” fast”.
    That pilot’s attitude caused ” Flutter” not to his tail but to the busy ATC guy who ” talks funny”.
    Stay as close to Va as possible keep your wings level and don’t test the airframe.
    Exercise common sense ….we can’t out climb the weather but wen go around it or make 180 back to VFR.

  • Regarding the statement: “…from that most recent event, it looks like the tail still fails first.”

    Apparently that opinion was formed by adding an old bias against V-Tails to the debris path description of the right ruddervator being in the first pile.

    The NTSB report states there were paint marks consistent with the left outboard wing striking the right ruddervator. If the “tail still fails first” statement is true for this accident, can Richard (or anyone) explain how the tail failed first and caused the paint transfer?

    The first pile also included overhead panel parts, yet no one is suggesting the overhead panel failed first. Wouldn’t a better theory be the left outboard wing failed first and hit the top of the fuselage then the right ruddervator, and thus liberating both panel parts and the ruddervator? That the wing landed 400 feet later is not a surprise (or a good enough reason alone to question the strength of a V-Tail).

  • When the tail is not doing what it was designed to do, it fails.
    That does not mean that it separates, then the AC is out of control and speed due to gravity becomes the cause of stress exceeding the G limits, at witch time the wing spars brake apart.

    • The complete sentence was: “The tails were required to be strengthened a while back but from that most recent event, it looks like the tail still fails first.”

      The tails being strengthened refers to the post-C models that had more tail surface area ahead of the spar and DID fail first, soon followed by the wing. The strengthening fix was to put a cuff on the leading edge of the ruddervator where it met the fuselage. Collins’ reference to that fix, along with his use of the phrase “still fails first”, betrays his thinking that the failure mode in the recent accident is identical to the ones from long ago which, incidentally, was always caused by the tail separating from the fuselage (first), and not some imaginary failure where it “failed” but stayed attached.

      Furthermore, when the tail failed in the early days, the wing failed in the down direction. The fact that pieces of the overhead panel were found at the beginning of the debris path implies the wing failed in the up direction and hit the top of the fuselage.

      Either your description of the tail failing without separating (whatever that is supposed to mean) is incorrect, or Collins connecting the old V-Tail failure mode to the recent accident is incorrect. Or, as I suspect, both are incorrect.

      Hopefully the NTSB final will say for sure.

  • Very good and well researched article.
    The measures taken by the FAA, instructors etc. surely are good and justified, but the root of the disaster in the initial examples was the vacuum pump and their numerous failures. So let’s eliminate the root cause of many fatal airframe failures by obsercance of one simple basic rule:
    Never ever turn the propeller backwards.
    The cross section picture of a vacuum pump above illustrates why: During operation the wings of the pump are dragged in an angle of more than 100° towards the axis. If you turn your propeller backwards, you force the pump to do so, too (via the accessory gear to which it is attached). This pushes the wings of the pump against it’s walls, where they can get stuck especially where the radius is narrowing, and the wings crack and break. So once again, dear pilots and mechanics:
    If you need to turn wour propeller, turn it forward only. Never turn it backwards if you don’t care for a surprise in IMC.

  • Years ago I was in flight test with another V tail aircraft (first was Have Blue) and the second was the follow on from proto through deployment – the F-117. Flutter tests were ALWAYS nail biters – and the time from flutter onset to “knock it off” was very short. You simply never want to get into a situation which induces flutter. This brought back some memories – and they weren’t good ones.

      • Hey Chris, I should have mentioned – I was on the downlink end of the telemetry stream – we were watching the data come in on the computer screens and strip charts – not in the test vehicle.

        Those guys were all incredible – I have never had the pleasure since, of working with test pilots of that caliber – consummate professionals, and I can tell you stories of missions gone sideways that you can’t believe happened – and/or ended well for the pilot. Flutter missions would bring the aircraft to the point of the onset of flutter and the “knock it off” before the control surface parted company with the fuselage (It was a very fine balance between getting the data and violent, destructive flutter – they had a T-38 or a A-7 flying chase and watching, and we could see the oscillation early on with the telemetry.

        The aircraft were equipped with recovery chutes in case the entire empennage tore off. It was very very dicey, but not something that at least in those days, could be modeled in the computer of the day, or in a wind tunnel – some brave jock had to put his but in the seat, and get the data. As a pilot, flutter still gives me nightmares, and I have the greatest respect for its effects on a control surface or an air frame.

        I have some time in a V-tail beech V-35, and though its a beautiful aircraft, it always felt a little “squirrely” to me in the yaw axis (probably just me and not the aircraft).

        My personal feeling about flutter is keep the aircraft well within its design envelope at all times – having seen up close and personal what flutter can do and its rapid onset, is something that locks in your brain. Rule of thumb: “Never fly a J-3 or a C-152 at close to mach” 😉

        In flight test, the guys are “paid” (well the Lockheed jocks anyway – the USAF guys get what they get from Uncle Sam) – for what they do and the risk they accept, and the aircraft specially equipped from a look ma no tail! scenario –

        But as pilots we would just wind up watching the altimeter unwind and the ground get bigger, Flutter = bad (very very bad) thing! — And MANY thanks to Mr. Collins for this article – and the information on dry vacuum pumps.

        I started reading his columns in Flying magazine as a kid in utter awe of anything with wings (I still am) Nothing prettier than a J-3 — except a stagger wing Beech – when I was young, I would cut Mr. Collins articles out and put them in a binder – I may still have them someplace

        • Cynthia, thanks again for the eye opening real life information !!!!
          Mr. Collins is a selfless life saving teacher, never had the pleasure of meeting him but I feel I do know him some by reading his great articles.
          His experiences are presented with honesty and humble attitude.
          One of my students once said : I have flown with a few instructors who are professors. You are a teacher, they…. profess to know.
          I was pleased to hear him say that not because of ego boosting on my part, but because he was open to receive knowledge. When students learn how to educate themselves with our guidance the fishing lesson will feed them for life.
          The closest experience to flutter for me was when I was teaching multi engine students in a B-58 Baron.
          Demonstrating power off stalls to students and have them practice was a great time to experience the feeling on the yoke at full stall. The feeling of surprise/ helplessness on their faces ….wow, a moment ago the airplane was responding to their inputs in an honest brisk way and now at the stall regime the tail section was almost useless to the point they can feel the presence of the counterweight.
          The only similarity here of course is the uncharted territory and by no means ” flutter” as we know it.
          Some aviation books were describing WWII pilots diving with full power only to see their wings depart from the fuselage.
          The graphics on the page got my attention.

          • Chris – those that can teach are very rare, professors are not so rare. In our lives – we remember the teachers – the professors – not so much. When I learned to fly I first had a professor – I got so nervous I couldn’t think – then I got a teacher – he let me (not to be zen) but learn to become one with the aircraft – I never felt nervous, he expressed confidence in me and guided when it was appropriate. I am quite sure that MR. Collins would be a teacher.
            I was kind of raised with a love of things with wings – dad flew B-17’s through hell over Germany. So I guess its in my blood- there is a very early picture of me – probably 5 or 7 years old sitting in an F-86 and the helmet was silly large on my teeny head – those were early memories. My best and most exciting memories (other than my solo in a c-150 way back when, at IDT back in Michigan ha!) was my years in flight test out where it doesn’t exist. – I not only got to work with and meet some of the finest test pilots on the planet (one fellow flew the shuttle after working on the black programs, another I believe did the first test flight for the B-787) I got to have lunch with an SR-71 jock *(and boy did I bend his ear!) – and see and respond to some crazy situations – I am proudly – a Baja Scorpion alumnus – if you google on the Baja Scorpions you will see some of what I’m talking about and some of the pilots – including a fellow by the name of Paul (USAF) – Paul was a really short little guy and got treatments like a telephone book on the seat and they stuck blocks of wood on the rudder pedals – but oh man could he fly. I think there is a picture of all the test pilots on the Baja Scorps web page….you can pick out Paul T without much trouble – If I recall, Paul flew some of the flutter missions – the only thing better than talking about flying is flying and learning more about flying to improve your flying LoL

  • Dry vacuum pumps have a terrible failure record, it’s hard to imagine that the FAA approves them. Dual pumps don’t always work, as the shuttle valve between them can leak so debris from a failed pump can get pulled into the standby pump causing it to fail also.

    Glass panels are expensive. Electric gyros can also be expensive and some are unreliable.

    Wet vacuum pumps are reliable. Although the new Airwolf wet pump is expensive, the old Garwin and Pesco wet pumps are reliable and overhauled units are reasonably priced.

    I find my Garwin wet pump powered AI and electric King KCS-55 HSI to be a reasonable combination that has proven to be very reliable. Although the HSI could be very expensive to repair, used replacement units are readily available since many are being replaced with glass.

  • I’m late to the discussion, but there is a point I’d like to make. I feel that part of the problem with vacuum pump failure is that many pilots fail to appreciate how serious an emergency it is when it occurs in IMC (or if IMC is encountered after a failure), or how one should try to conduct the flight following a failure.

    In the recent case of the V35 breakup over Long Island that Dick speaks of at the beginning of his fine article, the vacuum pump failure occurred while flying in VMC on top. The pilot then subsequently entered IMC while seemingly casually continuing the flight toward his original destination. Why? it seems to me that in such cases a concerted effort should be made to find a route to a landing that would allow one to avoid IMC as much as possible. That includes climbing if necessary to stay out of clouds ahead. If it is necessary to descend through IMC after vacuum system failure, it makes things a LOT easier if you avoid maneuvering as much as possible. What you want to do is establish a stable glide on a fixed heading so that maintaining control is basically a matter of keeping the wings level. Gear should be down, and possibly some flaps if that makes things more stable. If at all possible, make the descent to an area with VMC ceilings and visibilities so as to avoid the need for an instrument approach. Yes, all this will have to be requested and coordinated by ATC, but remember, it’s an EMERGENCY!

    And yes, a good backup AI can be a lifesaver in such circumstances, but it should be used only to make it easier to keep the wings level, not as a way to continue to fly in IMC as if nothing had happened.

  • The Vacuum Pump was a good thing back in the thirties. It was acceptable in the fifties when we knew no better, but we do not need it now!

    I use a single venturi mounted on the belly just aft of the exhaust pipe to power my ancient T&B, the only anachronistic thing in my panel.

    Back in the thirties when venturi powered instruments were common, the venturis were always mounted as mine is. I am an antique so it works for me, but modern electronics really do make any vacuum (or pressure) system totally unnecessary. Why not junk them all?

    Happy Skies,

    Old Bob
    (Soloed in 1946, IFR rated and actively flown since 1950)

  • When speaking of pilots losing control of airplanes because of the loss of attitude gyros, it is interesting to note that Charles Lindbergh flew from San Diego, California to St. Louis, Missouri at night over dark, mountainous terrain with no gyros whatsoever and no electrical system. He then continued on to New York in marginal weather. Then, a few days later, made his historic flight to Paris in low IMC weather – much of that at night – all with no gyros. So the obvious question is: Why do pilots today lose control of their airplanes when they lose their attitude gyros? Is it because of a failure to recognize such until it is too late to recover from spirals that break up the airframes due to over-stressing? All airplanes will fly just fine without attitude indicators while in the clouds using nothing more than what Charles Lindbergh had in his airplane. I believe the real failure is in the teaching of basic instrument flight. As instructors, we’re failing miserably in that department. An accurate scan, constantly comparing information received, will catch a failing instrument(s) quickly. We all know that. So let’s do more teaching in that regard. Teach basic-instrument flight with a system that will slowly “fail” the gyros, then have the students fly partial-panel until they can fly around all day long without the attitude indicator and directional gyro. When you teach in a simulator make it more realistic; make it noisy – loud music (multiple songs at once), background noises, distractions of all sorts… Bang on the side of the rig with a shoe if you have to, tell the student there’s a poisonous spider running around the box someplace and then go hunting for it while the student is shooting a difficult approach; make it as realistic as you can once the student has gained a “certain” level of proficiency. There are times when airline pilots are required to listen to three of four conversations at once and pick out the “meat” of each one…The loss of two gyros in IMC should not be that big of a deal. Train until you reach that level of confidence and then maintain it. That’s what a professional SHOULD do.

    • FYI, the Spirit of St. Louis had a T&B right in the middle of the panel. There are pictures of the panel on the Smithsonian website and other places.

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