More to it than meets the eye
Every pilot knows that cocktail napkins were invented so aircraft designers would have a place to sketch their wildest dreams before they start trying to certify that dream. What most pilots don’t realize is that certifying that exciting new design is but a small part of the picture. There’s financing, engineering, production and sales and, in the end, profit. If the latter isn’t possible all the rest can be for naught.
This is why I, for one, take the proposed rewrite of Part 23 certification standards not with a grain, but with a round blue cardboard container of salt. (Read John Zimmerman’s post on the Part 23 proposal for a different view of the subject.)
In the course of 57 years of private flying I flew just about every airplane certified under CAR Part 3 and FAR Part 23 that replaced it. I listened to a lot of folks complain about the cost of certification and I heard others say it never was a hindrance. I also ran up on a lot of things in certified airplanes that made me wish it had cost just a bit more.
These rules have withstood the test of a lot of time, though, and a lot of airplanes have been developed using these standards. I don’t think anyone would fault the development of airframes over this time period. The record has been excellent and when there have been airframe failures, with few exceptions they have come when the airplane was operated outside the envelope. The main exception I can think of came with the Cessna 441 turboprop. A structural problem with the horizontal tail came to light after it was certified.
I have known a lot of engineers at airframe manufacturers and none has ever complained about any specific Part 23 rules. I have read all of it and if you would do the same I think you would come away thinking that it is pertinent. I always felt that it outlined the kind of airplane that I wanted to fly. Yes, it is cumbersome in a bureaucratic sort of way and, yes, it could be simplified, but it is still a recipe for pretty good airplanes.
If, after it is certified, an airplane is deemed to have an unsafe condition the FAA issues an Airworthiness Directive (AD) that brings it up to snuff. If it’s really dangerous, the issuance would be an emergency AD which usually requires compliance before further flight.
ADs might be considered the grade on the quality of a certification. The more ADs, the worse the grade. There are usually more ADs issued when an airplane type is new. Often, shortcomings are not found until the airplanes are turned over to the real test pilots, the owners. We fly them and find out about glitches during normal use as opposed to test programs. Then, when airplanes get old, ADs might start showing up again but these usually relate to wear and not certification.
I think the P210 that I got new in 1979 had as many if not more ADs than any other new type. For a while it almost seemed there was an AD du jour. The systems on the airplane were not even close to being up to standard. Simply put, it came out of the oven before it was done. It slowly evolved into a reasonably reliable airplane.
Problems during certification have almost always come because, like any regulations, these are subject to interpretation and an over-zealous FAA person can be a real pain. At one point, the interpretations varied so much among FAA regional offices that the FAA hatched a plan to even things out by making lead regions for certification based on expertise in that region.
For example, airliners come mostly from the Northwest Region so that wasn’t a good place to certify a light airplane. Best let the Central Region handle that. I think the FAA’s work on this helped though interpretation of rules still plays a big part, which is true with all laws. If it wasn’t, we wouldn’t need a Supreme Court.
I’ll give you an example of a problem related to one FAA weenie’s interpretation of the rules.
I was at the Mooney factory in Kerrville, Texas, when they were working to certify the M20J (201). The FAA was giving them fits because on a go-around, when power was applied briskly, the engine would momentarily go about 50 revs above the red line and then come right back down. The FAA guy insisted that was not certifiable.
Roy LoPresti, who was chief engineer, asked me if I would help with this. I had a Cardinal RG at the time. It had the same powerplant as the 201. Roy asked if I would take the FAA man and one of his engineers flying and see how the rpm behaved in the Cardinal.
Guess what? The rpm momentarily went 50 over and then returned, just as Roy and I knew that it would. The Cardinal was certified in a different FAA region than the one where Mooney was located and that FAA person was still reluctant to sign the airplane off. Some negotiating with the regional office finally fixed this.
Problem solved, but it delayed the certification of the M20J by as much as a week while they worked the problem. Something like that would never be solved by a rule change. It took a kinder and gentler interpretation of the rules to get the job done.
In the Part 23 proposal, three areas seem to get special emphasis. All three relate to accident causes. One is important, two are far-fetched. Loss of control accidents, especially of the low-speed variety, are at the top of every safety list and this has always been and will likely always be a place where we work hard but with little reward. The other two address Vmc in twins and airframe ice. I’ll tell you later why I think these are far-fetched.
Could changes in the certification process help reduce the number of low-speed control losses? I don’t think so.
An in-flight loss of control is directly related to what the pilot does or does not do with the controls in the airplane. How the airplane responds to those controls is covered in the regulations but rather than setting this out in black and white, it is done in shades of gray because that is the only way it can be done.
Handling (or flying) qualities vary widely among airplanes. Even airplanes from the same manufacturer don’t always fly alike. Even the exact same airplane can have flying qualities that change markedly as the center of gravity changes.
Because a mishandling of the elevator control leads to a lot of low-speed loss of control accidents, let’s look at pitch control.
The rules say that an airplane must be stable in pitch. That means that if you pull or push away from the speed for which the airplane is trimmed, it will return to the trim speed. That is pretty simple except for two things. Moving the center of gravity aft diminishes pitch stability as does increasing power. The rules don’t say how stable the airplane must be.
One model of the Piper Cheyenne, the IIXL, offers a good example of how this works. Because one stability test must be done with climb power, Piper actually had to limit the allowable climb power of this airplane to pass the test. In other words you couldn’t use full power for climb.
What does this have to with low-speed losses of control? It is all related to the power of the elevator control to move the airplane deeply into a stall.
There is nothing new about using elevator control restrictions to try to cut down on low-speed loss of control accidents. Before World War Two Dr. Otto Koppen developed an airplane called the Skyfarer that was certified as being incapable of spinning. He used some patents developed by Fred Weick who developed the Ercoupe just a bit later.
The Skyfarer never made it into production. World War Two came along but hearsay suggested to me that it was not a pleasant airplane to fly. Fred Weick was able to develop the Ercoupe into a stall-resistant, spin-proof airplane that was commercially viable for a little while in the brief aviation prosperity after World War Two.
The Ercoupe did most of what is envisioned today by those who say the low-speed loss of control accidents can be designed out of an airplane. It didn’t really work, though, because the Ercoupe had a worse safety record than other two-place airplanes.
It doesn’t matter what you do aerodynamically; there is no way to eliminate the increase in drag as an airplane is slowed down. An increase in drag means it takes more power to fly and eventually the sink rate might outnumber the horsepower and the sink rate might increase to a disastrous level. That is also true the slower you go with no power. Technically, control of the airplane would not be lost though control of the sink rate might be considered as lost. If the hit is hard enough, it matters not if the ailerons were effective at the moment of impact.
I remember seeing pictures of fatal Ercoupe wrecks that looked almost like spin-ins.
I think that pitch stability has a lot to do with low-speed losses of control. The rules now say that the stick force must vary with speed so that any substantial speed change results in a stick force clearly perceptible to the pilot. That is apple pie and motherhood stuff but it is not precise.
The current rules take a stab at this by addressing stick forces. A maximum of 75 pounds with two hands on the wheel, 50 with one hand, and 60 pounds if the airplane actually has a stick are the greatest forces allowable. An airplane with the maximum allowable stick forces would require some grunting and groaning to do much maneuvering. On the plus side, if it were being flown too slowly that would be quite obvious until the stick forces were trimmed off.
The P210 that I flew for 28 years offers a good example of loading and stability. The airplane has an exceptionally wide cg range, from a forward cg of 37 inches aft of datum to an aft limit of 52. At forward cg, it would test those maximum allowable stick forces. At close to aft cg, you had to use your imagination to think that a speed change resulted in a stick force that was clearly perceptible to the pilot, as is required.
Just as a matter of interest there have been many STC’d mods for the P210 and to my knowledge none have been able to certify to that 52 inch aft limit. Most settle for 50. The farthest aft I flew mine was 50 and, given the handling qualities at that value, I had no curiosity about the other two inches.
The Cheyenne had stability problems because it was developed from the Navajo. There was a big horsepower increase that was destabilizing. To counter this, the original Cheyenne was certified with a variable downspring that started exerting nose-down force when the airspeed dropped below 125 knots and reached a maximum force at 100 knots. They called it a stability augmentation system.
In some other airplanes, the spring is just there all the time so it’s a plain old downspring. Either way, what springs do is, in effect, create artificial control feel. The rules just say it has to be perceptible. It does not have to be natural feel. And the springs can make it possible to add power to the airframe or increase the cg range and still pass the test. A later model of the Cheyenne was offered without the stability augmentation system. It had less power and a narrower cg range.
Because it is easier to intentionally stall an airplane with light pitch forces than one with heavy pitch forces, it is also easier to do so accidentally. Because buyers demand the widest possible center of gravity range there is really no way to say the pitch forces are required to be a certain value. Whether a prescribed range of pitch forces would help would be open to question.
The Skyfarer and Ercoupe were both stall resistant. Being two-place side-by-side airplanes, a narrow cg range was acceptable. The up-elevator travel could be limited so stalling would be limited if not impossible. That can’t be done on a four- or six-place airplane where a larger cg range is required if the airplane is to have practical value.
There is a lot more to improving low speed handling qualities than tinkering with the regulations, or the wing, so best avoid just those low altitude losses of control with appropriate bursts of brilliance and superb flying technique.
Angle-of-attack instrumentation is mentioned as a way to help on this.
Not long after I started flying, the CAA (predecessor to the FAA) instrumented a Cub with a five light system that displayed angles of attack. If I remember, the goal was to fly the approach with the middle light on. The same was true for climbing.
I think a current Part 23 regulation came from this research. It says that a visual stall warning device that requires the attention of the crew within the cockpit is not acceptable by itself. That means even with AOA, the airplane has to have a natural or aural stall warning (either of which is really is a single angle of attack indication). It might help to increase the current five knot minimum airspeed for a stall warning. In maneuvering flight in an airplane with light stick forces, that five knot minimum might lead to a beep-boom end to the day. Maybe ten knots would work better,
When my father started Air Facts in 1938, a key area of emphasis was the stall-spin accident. So there is nothing new about any of this. That doesn’t mean it should not be continually addressed but the potential solution has always been found to reside in the pilot.
Another focus area is Vmc in small twins. I think it is great they are addressing this because it has been a hot-button issue for me since July 22, 1958. On that day I lost friends in what I think was the first Vmc related fatal accident in a light twin, a Beech 95 Travel Air.
That accident was followed by an alarming number of similar accidents in Piper Twin Comanches and Beechcraft 95s and Barons. Some of the most experienced multiengine instructors in the country were lost in these accidents which were a direct result of what the FAA required in multiengine training (Vmc demonstrations at low altitude).
Those accidents slowly faded from the scene as the FAA required maneuvers were changed, as popularity of twins dropped, and as the main multiengine trainer became the Piper Seminole with a few Beech Duchesses also on the line. These airplanes have impeccable engine-out manners because they were designed with the previous problems in mind.
I’m all for improving the handing qualities of new multiengine designs but only a handful of new twins are sold every year so I hope a lot of sleep isn’t lost on this. It’s not a matter of the FAA being a day late and a dollar short, it’s a matter of the FAA being 58 years late and a dollar short so how come it is a big deal now?.
And there is one icing bugaboo on the agenda, supercooled large droplets, SLD. The FAA apparently discovered this when a turboprop airliner was lost because of airframe icing.
I just looked up heavy icing in my 51 year old copy of Aviation Weather. It is described as icing that continues to accumulate despite de-icing procedures. It is critical from the standpoint of flight safety. In other words supercooled large droplets are new buzzwords for something we have known about for years. Doing such is how bureaucrats try to justify their existence.
Ice is a completely different subject for light airplanes than it is for jets. I flew a light airplane for 28 years that was approved for flight in icing conditions and I am here to tell you that such an approval is a real booby trap for gullible pilots. They put a patch on this a while back with an AD that required flight manual additions that acknowledged icing conditions exist that the equipment can not handle. I think this tells you that a blanket approval for flight in icing in a light airplane is dangerous. It makes no more sense than would approval for flight in thunderstorms.
That said, I sure did like having the ice protection equipment. I knew its limitations and followed the same procedures I used for years without ice protection: at the first sign of ice, do something to get out of that ice. Icing equipment in light airplanes is a valuable tool to use while you go for help.
So, addressing heavy or severe ice, or SLDs, is beside the point for most private pilots. The only thing that can help with that is action from the PIC.
A positive recent development not related to the Part 23 proposal has been the approval of some non-FAA approved electronic devices for certain airplanes under an STC obtained by EAA.
Hi-tech cockpits shouldn’t also be high-bucks because of tedious approval processes. The most significant development for general aviation cockpits has come from the iPad which you can buy anywhere and carry with you in any airplane. The aviation programs that are available for the iPad can bring an almost unheard of level of capability to an airplane that doesn’t even have an electrical system.
Really good and relatively inexpensive installed avionics have been available for experimental airplanes and there is great promise in the approval of this equipment in certified airplanes.
Back to Part 23. There is no harm to be found in a review and possible simplification of these rules. If common sense prevails, though, the airplanes that are developed will be much like the airplanes that came from the existing rules. There’s just too much good history there to ignore and when all is said and done I don’t think it will be ignored. Also, a change in the attitude of FAA personnel as they interpret regulations might do more to help than anything else.
Don’t count on flying becoming less costly, though, and don’t look for any improvement in the safety record. Noble as those causes may be, they have always been elusive.