I have written this piece with the intention to bring awareness before a large statistic is created. This article has been forming for quite some time. Please take it as a mild wakeup call before greater catastrophe happens. I see this topic much as I saw things happening in 1998 when I began speaking out on jump plane safety. It is NOT a piece to condemn the pilots or operations mentioned here. Everyone was doing the best they could at the time things happened.
Dear aircraft owners, pilots, and DZOs,
I think there is a growing problem. Since 2008 I have been monitoring several single engine turbine accidents and incidents. Most have been Caravans, but there are a few reports of PAC-750s. The problems seem to stem from the concept that a single engine turbine is just a step up in power over a single engine piston aircraft. However, the types of accidents I am seeing leads me to believe that not enough information is being shared and training has been inadequate for the growing number of single engine turbine aircraft in the skydiving fleet.
Any engine failure soon after takeoff WILL be a very stressful event. Training must be thorough and review should be accomplished with regularity on the procedures from the PIM/POH/AFM. In 2008, a Caravan lost its engine during climb due to blade creep. The NTSB sited the owner/operator for poor maintenance leading to the failure. We can all take a long period pointing fingers on what caused the engine failure to begin with, but what I’m concerned about is what the pilots are doing AFTER the engine fails. Several engine-out events have led to accidents with major structural damage or total hull loss. There are two paths to poor outcomes happening here.
FEATHER PROP AND OVERSHOOT RUNWAY / SUITABLE LANDING AREA
Some pilots are following the PIM and feathering the propeller according to procedure. They have had plenty of altitude almost directly over the airport. However, they have come in too fast (and in a couple of cases downwind) and overshot the runway ending in substantial damage. When these accidents happened, I put out several calls for Caravan operators to have their pilots practice with a ZERO THRUST SETTING approach to simulate a feathered prop. You will not have the normal drag of a windmilling prop to slow you down. The descent angle will be much flatter and if you try to fly target altitudes and speeds around the landing pattern, like a normal post drop approach, you will overshoot almost every time. After consulting many experienced jump pilots in Caravans, it has been suggested that a setting of 300# torque will approximate a zero thrust or “feathered” propeller. You do NOT want to actually feather the prop for practice and land it, as you will be creating a real emergency. This is for demonstration and recurrent training of your single engine turbine pilots.
Understand that the Caravan PIM states that with an engine failure after takeoff, the airspeed of 85 KIAS should be maintained, prop feathered, then flaps to 20 degrees recommended. This is to preserve speed and altitude as much as possible. Otherwise the now non-powered prop will be creating more drag than idle power descent! Fuel condition should be cutoff (to take away any more fuel that could be burning up there before crashing). These things must must must be ingrained and acted upon. The term “turbine safety” may be true and a nice selling point in acquiring a single engine turbine aircraft for your jump operation, but for the pilot stepping up the decision tree, it becomes a lot more complex.
DID NOT FEATHER AND CRASHED SHORT OF A GOOD LANDING AREA
As mentioned previously, the PIM states that the first action after maintaining flying speed should be prop feathered. However, several recent accidents show that pilots don’t always follow the book and it can create a consequence that, while might not fatal, could very well lead to hull loss.
Set up initial and recurrent training for your pilots to discuss, practice and execute emergency procedures or the intensity of the situation may overwhelm the pilot. Some may call it tunnel vision (stress induced vision loss), but more likely it is “tunnel thinking.” FLY THE PLANE FLY THE PLANE FLY THE PLANE. And with that they may corner themselves into decision-making that has a less than optimal outcome.
Two recent Caravan accidents had an engine failure that began around 2 thousand feet above the ground. No skydivers left the aircraft (which I will discuss as another issue later). However, the prop was not feathered. In one case, the descent rate with a wind milling non-feathered prop was 2000 feet per minute or more. The pilot, obviously sensing the great drag of the prop, also flew an indicated airspeed well above the recommended 85 KIAS, possibly trying to ensure that he did not stall and spin. If the pilot chose to leave the prop not feathered so as to have drag during rollout, then by that logic adding flaps would have helped reduce energy at touchdown thus reducing ground roll. But the pilot also did not use any flaps (also contrary to the PIM which calls for flaps 20 degrees). Again, I have trouble actually faulting the pilot for not perfectly following the PIM procedure. I wasn’t there, do not know his experience level and do not know exactly what altitude the emergency actually started at. But taking this action (or non-action as it were) the time for decision-making and approach setup were greatly reduced. This is why procedure needs to be instinctive. You do not rise to the occasion you fall to the level of your training.
TWO THOUSAND FEET AND NO ONE JUMPED
In two recent cases, the engine failure happened at or about 2000 feet above field elevation. For the longest time in skydiving I’ve heard the mantra (with a little bravado) “just get me a grand and I’ll bailout on reserve,” yet no one did. Now, jumpers are trained that in an aircraft emergency, they should prepare according to instruction from the pilot. However, we have seen that in these, now more complex, single engine turbine aircraft, the decision tree is more complex than a single piston engine aircraft. Things happen faster and if exacting action is not taken at the right moment, the time until touchdown is greatly reduced. Suddenly jumpers are shouting questions at the pilot and they may very well get no response due to the pilot, who is already task saturated, concentrating on just keeping blue up and brown down. So discuss it now on the ground with your staff, your experienced jumpers and then train your newer jumpers. Keep in mind that bailing above one thousand feet above ground may work in piston singles, but if you don’t start out with an engine failure well above that altitude (I’m saying 4-5K) you realistically won’t expect anyone to get out. The best things to do unless the plane is out of control, is ensure the security of the seatbelt/restraint and secure your helmet (preferably on your head). Do nothing until the aircraft comes to a stop. I know in this situation emotion can run very high, but while a recent jump plane landed off airport, a jumper can be heard yelling “open the door! open the door!” while the plane is still speeding along trying to stop. Discuss with jumpers that taking this action would require a jumper to move out of a good brace position, thus exposing themselves and others to injury if the aircraft collides with say a truck or tree.
Each emergency situation is unique, but through discussion, training, recurrent training and after incident analysis we can improve everyone’s knowledge and chances for survivability should the remote chance of engine failure lead to undesirable states of landing.
In summary:
- Train pilots on the proper procedure for engine failure from your specific aircraft pilot manual. Make sure everyone is on the same page on how an engine failure will be handled.
- Discuss with your pilots and ESPECIALLY visiting pilots on where good terrain is in case of off airport landing should become necessary.
- Have the pilot practice zero thrust landings simulating feathered prop with both zero flaps and normal landing flaps (or recommended flaps during engine failure per the PIM). Make it a part of recurrent training also.
- Discuss with your jumpers on the idea that old adages of skydiving plane emergencies may not work now with the proliferation of single engine turbine jump planes.
Unknown:
2016 Skydive Mexico crash
Please join our FaceBook Group for further discussion or leave a comment here.
2 replies on “Addressing Single Engine Turbine Accidents.”
Dear Skydivers,
I understand your concern about engine failure on a single turbine engine. The pilots’ job and responsibility is, to take the skydivers in to the air safely. To land a single turbine engine plane with an engine failure must not end in crash with a total loss of the plane. There are some survival factors which help not to end in a disaster, like pilot experience, terrain, altitude of the engine failure, weather. I have joined as a pilot in this business 4 years ago.
I operate a PC-6 Pilatus Porter and I have to renewal my current class rating every two years with an examiner of the national authority. On every check flight the examiner wants to see the emergency handling of the airplane like, engine failure after take-off, engine failure in flight.
The focus of him is usually, that I apply the correct checklist of the airplane flight manual (AFM). The AFM has two items on it: In case to do an airstart: Normal relights and immediate relight.
Well, the checklist is good as far you have enough height above the ground. Especially the normal relight procedure takes a while to restart the engine and the PC-6 loss in empty condition around 1500 Ft on height until the engine is on full power again. So you can’t apply that near to the ground.
The immediate relight procedure would work more, but can also end close to the ground in a disaster .The first task would be to turn the starter and ignition “on” after flame out. You can pray that the engine will start up, but in these short seconds you don’t know what turns the engine off. It’s better as Pilot you don’t waste your time to the engine. The problem is that propeller has in Climb a small propeller angle. In this condition, if an engine failure happen the propeller works as a break, so the plane will lose speed additionally thru the propeller. If the Pilot doesn’t act with a Pitch nose down, the plane would go immediately in a stall. I don’t now other turbine engine airplane work after engine failure, but by a PC-6, you should close to the ground set the Propeller to feather and nose down immediately immediately, so you prevent a stall.
Now, the big question in this situation is what for opportunity as Pilot do you have to land the plane into terrain. If you have flat cut grass field, Corn field without obstacles then your chance to survive is very high. Wooded, populated areas will reduce to survival chance.
The question to use the Flaps is not always helpful. The PC-6 has the best glide Speed of 75 Kt in clean configuration. To use the Flaps helps when you have to go in high angle into terrain otherwise let it be.
The rise your chance to survive an engine failure depends on altitude. If I have passed the circuit altitude or higher in Downwind leg I would glide back to the airfield. If I’m below let it be and focus to land into terrain. I would give the signal to the Skydivers to exit about 1500 Ft or higher.
So you can see it’s not always guarantee to land safely when you follow the Checklist of the AFM strictly.
With kind regards
Steven
Hello Stefan. Keep in mind it is not skydivers running this site. I am a pilot and I have a group of highly experienced jump pilots I consult with regularly. This blog post was formulated from information on many accidents over the last ten years. Following proper procedure is important and the thrust of this post. Going “off script” just because you can doesn’t mean you have chosen wisely. That’s the problem I believe that is leading to these accidents. The script isn’t even known or taken seriously. Just saying “hey we walked away” is not good enough. If you are going to get in these vehicles we are paid to properly operate you have to be ready for any eventuality. Training is key. Regular recurrent training is also a major player.