The flight, in a TBM 700, looked like a piece of cake. The weather appeared good and, in fact, there was no record of the pilot even bothering to get any weather information. There are, however, many ways to check weather without creating a record.
The flight started at Teterboro, New Jersey, and was bound for Atlanta. The sky was clear at Teterboro and there was a surface cold front just to the south. Nearby Morristown, N. J., was reporting ten miles visibility with a ceiling of 20,000 feet. The surface temperature was plus six C.
As is almost always the case in the cold months, there was an Airmet for icing. The current Airmet called for moderate icing to FL200. An earlier one had the same but with the top of the moderate icing at FL180.
Pilot reports told a grimmer tale. In the time before takeoff, there had been reports of severe icing from a Citation and an MD-83. One report put the condition between 13,000 and 14,000 feet; the other between 14,000 and 16,500 feet. One of the crewmembers of the MD-83 said it was the worst icing he had seen in 38 years of flying and that he had never seen ice accumulate so quickly.
There were definite warning signs but nobody knows whether the pilot was aware of any of this.
The tendency when you are flying a high-performance airplane like a TBM 700 is to head out, planning to vault up into the sunshine in no time at all. This pilot had filed for Flight Level 260 which would be well atop the icing covered by the Airmet.
When the airplane was passing 8,000 feet for 10,000 feet, the controller cleared it to 14,000 feet and advised of moderate rime icing from 15,000 to 17,000 feet with light rime ice at 14,000 feet. The controller asked the pilot to advise if the icing got worse and the pilot responded, “We’ll let you know what happens when we get in there and if we could go straight through, it’s no problem for us.”
Ten minutes after the pilot had called ready for takeoff, the flight was cleared to 17,000 feet where the pilot was told light icing would be encountered. The pilot reported that he was entering instrument meteorological conditions when climbing between 12,800 and 12,900 feet.
When the airplane was at 16,800 feet with a groundspeed of 101 knots, the pilot said “Light icing has been present for a little while and a higher altitude would be great.” Not many seconds later, the pilot reported, “We’re getting a little rattle here can we ah get ah higher as soon as possible please.” Twenty-five seconds later, the pilot was cleared to FL200. A minute and nine seconds after that, the airplane reached an altitude of 17,800 feet before it turned left and entered a descent. Twenty-one seconds later, there was a final abbreviated transmission that included the word “declaring.” The final radar return, less than a minute later, was from 2,000 feet. That was only about 17 minutes after the pilot reported ready for takeoff.
Witnesses reported seeing the airplane descending at a rapid rate, shedding parts, and a wing was reported as missing.
A Bombardier CRJ crew operating in close proximity to the TBM 700 reported that their wing anti-ice system could not keep up with the ice accumulation and that 2.5 inches of ice collected on protected surfaces and four inches on unprotected surfaces, all in about five minutes.
In its infinite wisdom, the government approves properly equipped airplanes for flight in icing conditions and then defines severe (or heavy) icing as that which can’t be handled by deicing equipment.
The NTSB’s probable cause: “The airplane’s encounter with unforecasted severe icing conditions that were characterized by high ice accretion rates and the pilot’s failure to use his command authority to depart the icing condition in an expeditious manner, which resulted in a loss of aircraft control.”
I was talking with Mac McClellan about this. Between us we have flown well over 30,000 hours, most of it IFR, and we have seen a lot of ice while flying some of the frostiest routes in the eastern United States. But between us, we came up with only a few truly memorable ice encounters. That would be one where you could hear the angels singing. That we both survived is self-evident and what we learned was you need to go as fast as possible while getting out of ice even if it means sacrificing altitude. We also learned over the years that there is a lot of ice that can be flown but you do have to pick and choose and always have an “out.”
Which brings us to the TBM 700 pilot: He had reported 1,400 hours on his last medical application. That doesn’t qualify as inexperienced, but there’s no question that there was much out there he hadn’t seen yet. There were stern warnings about ice in the pilot’s operating handbook including word that ice could degrade the performance and controllability of the airplane. Mention was also made of ice forming aft of the protected surfaces. He had likely seen some ice before and dealt with it handily but on the fateful day he found the worst possible ice scenario. Such is rare but it does happen.
There was plenty of ice-free air down below so there was an out but his mind was on climbing and this was pushed too far. Following a low-speed loss of control, the airplane apparently entered a spiral dive, which is characterized by an out-of-the-envelope, high airspeed, high-g, steep bank with the airplane corkscrewing toward the ground at a rate of descent well in excess of 15,000 feet per minute. A pilot would have to understand the nature of a spiral dive as well as the only possible path to a successful recovery to make it through that.
I’ll tell you the theoretical recovery procedure in a bit. Rest assured, it is not taught.
The last two-thirds of the final spiral was likely clear of clouds with that recovery theoretically possible. For a relatively inexperienced pilot, though, it would be akin to trying to put the proverbial egg back together.
I wrote about a King Air accident that occurred many years ago where the overloaded airplane in climb picked up such a load of ice aft of the deice boots that the airplane simply wouldn’t go on any more. This pilot remained more or less in control of the airplane but the impact was too much for the occupants.
I think it was after this accident that manufacturers started publishing a minimum speed in icing in the POH of airplanes with approved equipment.
Over the years there have been other en route icing accidents, almost always characterized by a loss of control. In reading the reports many of the control losses seem to stem from the pilot being distracted by the icing, to the neglect of flying the airplane.
The more common icing accident comes after the pilot gets out of the ice and is maneuvering for landing. It is a given on most airplanes that flaps are not to be used with ice on the airplane and that you need a lot of extra speed on the approach. Apparently some pilots don’t take this seriously enough.
How much extra speed is enough? I flew a severe-ice simulation in a Cessna 208 (Caravan) simulator a while back and it illustrated the challenge found here. With the boots firing away almost continuously and with a determination to maintain a safe airspeed (I think I picked 140 knots) I got the airplane squared away on the ILS with the glideslope intercept coming at about the time the airplane was going to start down of its own accord.
In a condition like that, it was pretty plain that if the airplane went below the glideslope, school would be out. To that end, I remember the simulator instructor telling me that I was over-temping the engine on final. My apologies to Pratt & Whitney because I was going to do whatever was necessary to keep the airplane on the glideslope and if the engine would produce the power, I was going to use it.
It worked. I broke out of the simulated icy clouds and made a hot landing on a long runway. I didn’t start reducing power until I was close to the runway.
I think that icing simulation came from a Caravan accident where so much ice accumulated that the airplane could no longer maintain altitude. That Caravan had boots. The airplanes can now be fitted with TKS (weeping wing) systems and if a Caravan pilot reads this I would be interested in any comparison of the ice ability of the airplane with TKS v. boots.
I flew my P210 for 28 years and close to 9,000 hours. It had a boot system that was approved for flight in icing condition (the word “known” was not in the icing approval) and I never cancelled a trip because of forecast icing. Mainly I would go look and think of the boots as something to use while I was getting the airplane out of any icing condition that was encountered.
A high-wing airplane does have a definite advantage in ice. The accumulation aft of the protected surfaces that is always mentioned is on the bottom of the wings. I could see the bottoms of my wings.
When you are flying in cold clouds it is important that you know a lot more about the meteorological moment than is covered in testing and training but I will leave that subject for another day.
Finally, I told you I would share with you the theoretical recovery from a spiral dive. A Cessna engineer once told me that the only airplane they ever did an intentional spiral dive in was a T-37. (Maybe our Cessna historian, Harry Clements, remembers something about this.)
My information on this came from a Beech engineer. Apparently they had given a lot of thought to the subject because of the high spiral dive involvement of V-tail Bonanzas in years past.
In theory at least, an airplane reaches an equilibrium in a spiral dive. The g-load might be in excess of the limit load factor but not the ultimate load factor. There is no history of airframes failing in the spiral itself, only during an attempted recovery.
With high airspeed, the first recovery step is to level the wings. That would be true in a spiral dive but what happens next is the problem. When the wings are leveled the airplane will then seek the speed for which it was trimmed before control was lost. In a theoretical spiral recovery the g-load would stay the same when the wings are leveled. It would not increase. Theoretically the airplane won’t break itself so once the wings are level the pilot has to not apply any elevator force because that would disturb the natural course of events.
It goes without saying that the zoom would be spectacular but if power were reduced to idle, as it should be, the speed would dissipate rather quickly and normalcy could be regained.
I never tried that because I learned early on that keeping the wings level is a key to everything in aircraft control. A loss of roll control can only lead to ever-worse things.
An icing article in Air Facts many years ago had a fine title: “Ice is not Nice.” Truer words were never spoken. Do you have any icing war stories?