My first crash
Thread Starter
My first crash
1) As it might be reported by a local pilot, sipping a drink at the bar's terrace:
" the microlight made a normal approach and circuit. Seemed a bit high and fast, though, on finals. Perhaps a pilot who is used to runways longer than our 250 m? Touchdown was at perhaps 40% of those 250 m. That could still have worked out ok, but immediately after touchdown the engine was heard to rev up again, the craft slipped off the runway sideways and came to a halt just across the concrete access road."
2) as the pilot saw it happen:
"the flight had been eventless, and no problems were to be expected. I had landed here before, visibility was excellent after the morning's haze that had lasted till noon, and scarcely any wind. I must have been less than perfectly concentrated though, as I observed I was rather high on finals, and quite fast too. But nothing to really worry about, the landing was quite acceptable. I let the craft roll at leisure and began to steer right to vacate the runway, when suddenly the engine revved up again without my ever doing anything with the throttle. I only realised the alarmingly increasing speed when it was too late, my only good reflex was to steer left for all I was worth, or I might have ended in the clubhouse. Quite stupid not to cut ignition as soon as things went wrong."
3) same pilot, after recollection:
"I had already done a nice round trip earlier that day, 50 mins to go and 60 to come back, and with the hazy weather that must have been more stressy than I realised. But it was my first flyable day since far too long and I was going to fly and fly as much as I could ever manage. For this second excursion I had originally planned EBTX Theux as a destination, but learned on the phone it was closed for runway maintenance (see how useful ppr can be?) So I choose EBLN Liernu, not very far away and a field I had already visited. I must certainly have been too relaxed, and have underestimated the difficulty of the shortish runway (I am used to having 700 or even 900 meters). I did realise I was rather high on finals, and sideslipped a good deal. I really should have decided to go around, but tunnel vision had already set in, there was no idea of a plan B in my muddled head. The landing actually wasn't bad, here came my next error, to think all was accomplished once the wheels had touched grass, and let my concentration, or what remained of it, slip away. The engine revved up again, I suppose the throttle overcame the adjustable friction by bumping from the rough terrain. When the plane was first flown, there had been some difficulty in closing the throttle fully, this was much improved by slackening the throttle friction. Too much, I realise now"
4) root cause analysis and lessons learned:
Mental fatigue was the root cause, I should not have taken off for the second trip. Perhaps not even for the first. There should be a way of objectively assessing one's mental strength before deciding to fly.
As a secondary point, the throttle friction adjustment is delicate and critical. Note this is on a Rotax 4-stroke, where springs on the carbs pull the throttle wide open and this friction control is the only counterforce.
5) corrective actions:
5a) pilot must become a better pilot
5b) will need to buy a new prop; I was after acquiring a cruise prop anyway but should have liked some more time. This will be the most expensive part.
5c) engine and reduction gear will need careful inspection, and repair as necessary. Here is most incertitude, I just hope the engine is not too bad as it is very new with just 40 hours run.
5d) the nosewheel leg is to be rebuilt from scratch. Though all fibreglass parts survived unbroken (wheel fairings and engine cowling are intact) this will involve must work, but I can luckily count on some knowledgeable and experienced fellow pilots.
" the microlight made a normal approach and circuit. Seemed a bit high and fast, though, on finals. Perhaps a pilot who is used to runways longer than our 250 m? Touchdown was at perhaps 40% of those 250 m. That could still have worked out ok, but immediately after touchdown the engine was heard to rev up again, the craft slipped off the runway sideways and came to a halt just across the concrete access road."
2) as the pilot saw it happen:
"the flight had been eventless, and no problems were to be expected. I had landed here before, visibility was excellent after the morning's haze that had lasted till noon, and scarcely any wind. I must have been less than perfectly concentrated though, as I observed I was rather high on finals, and quite fast too. But nothing to really worry about, the landing was quite acceptable. I let the craft roll at leisure and began to steer right to vacate the runway, when suddenly the engine revved up again without my ever doing anything with the throttle. I only realised the alarmingly increasing speed when it was too late, my only good reflex was to steer left for all I was worth, or I might have ended in the clubhouse. Quite stupid not to cut ignition as soon as things went wrong."
3) same pilot, after recollection:
"I had already done a nice round trip earlier that day, 50 mins to go and 60 to come back, and with the hazy weather that must have been more stressy than I realised. But it was my first flyable day since far too long and I was going to fly and fly as much as I could ever manage. For this second excursion I had originally planned EBTX Theux as a destination, but learned on the phone it was closed for runway maintenance (see how useful ppr can be?) So I choose EBLN Liernu, not very far away and a field I had already visited. I must certainly have been too relaxed, and have underestimated the difficulty of the shortish runway (I am used to having 700 or even 900 meters). I did realise I was rather high on finals, and sideslipped a good deal. I really should have decided to go around, but tunnel vision had already set in, there was no idea of a plan B in my muddled head. The landing actually wasn't bad, here came my next error, to think all was accomplished once the wheels had touched grass, and let my concentration, or what remained of it, slip away. The engine revved up again, I suppose the throttle overcame the adjustable friction by bumping from the rough terrain. When the plane was first flown, there had been some difficulty in closing the throttle fully, this was much improved by slackening the throttle friction. Too much, I realise now"
4) root cause analysis and lessons learned:
Mental fatigue was the root cause, I should not have taken off for the second trip. Perhaps not even for the first. There should be a way of objectively assessing one's mental strength before deciding to fly.
As a secondary point, the throttle friction adjustment is delicate and critical. Note this is on a Rotax 4-stroke, where springs on the carbs pull the throttle wide open and this friction control is the only counterforce.
5) corrective actions:
5a) pilot must become a better pilot
5b) will need to buy a new prop; I was after acquiring a cruise prop anyway but should have liked some more time. This will be the most expensive part.
5c) engine and reduction gear will need careful inspection, and repair as necessary. Here is most incertitude, I just hope the engine is not too bad as it is very new with just 40 hours run.
5d) the nosewheel leg is to be rebuilt from scratch. Though all fibreglass parts survived unbroken (wheel fairings and engine cowling are intact) this will involve must work, but I can luckily count on some knowledgeable and experienced fellow pilots.
Last edited by Jan Olieslagers; 21st Mar 2012 at 18:50.
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Oops. Thanks for sharing.
For me personally, the flight is over once the engine has shut down, not earlier. So my hand will be on or near the throttle at least until the aircraft has slowed down to walking speed, and I try to keep distractions such as shutting down stuff, to a minimum.
As far as the engine inspection is concerned, I'm given to understand that the Rotax, after a prop strike, only needs the gearbox inspection, not a complete teardown of the crankcase assembly. This is because the gearbox provides pretty good insulation against the shock loads caused by a prop strike. But you'd have to verify that with a competent engineer.
For me personally, the flight is over once the engine has shut down, not earlier. So my hand will be on or near the throttle at least until the aircraft has slowed down to walking speed, and I try to keep distractions such as shutting down stuff, to a minimum.
As far as the engine inspection is concerned, I'm given to understand that the Rotax, after a prop strike, only needs the gearbox inspection, not a complete teardown of the crankcase assembly. This is because the gearbox provides pretty good insulation against the shock loads caused by a prop strike. But you'd have to verify that with a competent engineer.
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I am sorry to hear that Jan,
Not sure why the engine Rev-ed up again, but it sure is a good idea to find your own faults in this incident. A lesser person would have blamed the engine controls and come home with their ego in tact. This has made you a better pilot though, I'm sure.
Lick your wounds, patch her up and fly her as soon as (practically) possible; that will get you passed this hangover!
###Ultra Long Hauler###
Not sure why the engine Rev-ed up again, but it sure is a good idea to find your own faults in this incident. A lesser person would have blamed the engine controls and come home with their ego in tact. This has made you a better pilot though, I'm sure.
Lick your wounds, patch her up and fly her as soon as (practically) possible; that will get you passed this hangover!
###Ultra Long Hauler###
Sorry to read & see the damage, brave of you to come clean.
But I think the prop damage is looking slight enough just to need new individual blades (If you can). It's happened here twice to the same Rotax 912 UL without more than a dial gauge check !
On my own 912 the original builder put the carb. springs on for conventional opening which I've been pleased to have; perhaps that's worthy of swapping over ?
[And like someone else mentioned we were taught to keep hand on throttle control].
mike hallam.
But I think the prop damage is looking slight enough just to need new individual blades (If you can). It's happened here twice to the same Rotax 912 UL without more than a dial gauge check !
On my own 912 the original builder put the carb. springs on for conventional opening which I've been pleased to have; perhaps that's worthy of swapping over ?
[And like someone else mentioned we were taught to keep hand on throttle control].
mike hallam.
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10/10 for post event analysis and declaration.
I cannot imagine ever voluntary taking control of any machine, even a lawn mower, where the throttle default is wide open.
This was an accident waiting to happen in my view.
I cannot imagine ever voluntary taking control of any machine, even a lawn mower, where the throttle default is wide open.
This was an accident waiting to happen in my view.
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Jan,
Sorry to read about your incident. If you have a slipper-clutch (limitateur de couple?) and a carbon prop, you do not need to worry about your gearbox or engine. A wooden prop and no slipper clutch would be another matter.
Donald
Sorry to read about your incident. If you have a slipper-clutch (limitateur de couple?) and a carbon prop, you do not need to worry about your gearbox or engine. A wooden prop and no slipper clutch would be another matter.
Donald
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May all your prangs be little ones. After 30 years of flying, I have been embarassed - and lucky - only 3 times. We are fortunate to have learned more about ourselves from experience; the only damage to our pride and pocketbook.
Glad to hear you came out of it OK, and hoping you get in the air again soon.
p.s. - I thought the default for most aircraft was for throttles to open in case of a control cable failure?
p.s. - I thought the default for most aircraft was for throttles to open in case of a control cable failure?
Thread Starter
The plane and the owner/pilot being restored to some basic stability, repairs are the next tackle.
Prop: all three blades are broken, either acquire three new blades or acquire a new prop outright. The remnants do not mention any make or type, which I find a bit smelly. Better get a new prop, I feel as yet. Or...?
Nose wheel leg: to be investigated, but it looks like some parts will have to be acquired from the factory.
Ideas welcome!
Prop: all three blades are broken, either acquire three new blades or acquire a new prop outright. The remnants do not mention any make or type, which I find a bit smelly. Better get a new prop, I feel as yet. Or...?
Nose wheel leg: to be investigated, but it looks like some parts will have to be acquired from the factory.
Ideas welcome!
I have a 912S.
As I understand it the throttle was arranged thus so that in the event of cable failure the engine would run, (and presumably could be controlled the old way, on the mag switches.) The probability of cable failure was considered higher than that of spring failure.
On my aircraft I, like most owners of our type, have reversed the throttle connection. While I have had three throttle springs go in autos, I have only had one cable go, and those cables were never inspected. (The inner rusted through.)
Most 912Ss have a clutch to preserve the engine against drive train shock, and inertial forces (Though mine doesn't, it was made in a short window when they were not installed.) Luckily Jemima is a pusher and the prop is well away from the ground, though one of our number struck his prop on his pylon this week. Apparently there is up to 4" tip displacement under certain circumstances!
As I understand it the throttle was arranged thus so that in the event of cable failure the engine would run, (and presumably could be controlled the old way, on the mag switches.) The probability of cable failure was considered higher than that of spring failure.
On my aircraft I, like most owners of our type, have reversed the throttle connection. While I have had three throttle springs go in autos, I have only had one cable go, and those cables were never inspected. (The inner rusted through.)
Most 912Ss have a clutch to preserve the engine against drive train shock, and inertial forces (Though mine doesn't, it was made in a short window when they were not installed.) Luckily Jemima is a pusher and the prop is well away from the ground, though one of our number struck his prop on his pylon this week. Apparently there is up to 4" tip displacement under certain circumstances!
(and presumably could be controlled the old way, on the mag switches.)
Fail-full-throttle carbs is also normal, certainly on the 4 stroke Rotaxes. Makes perfect sense to me - wherever it fails, I would be happiest with a stuck full throttle, since I can always turn the engine off once in gliding range of something I can land on. I'd rather be forced to climb or execute an unexpected go-around than land NOW.
G
I was thinking that using the mags like the old blip switch on no-throttle engines was what was meant - controlling the engine revs by repeatedly turning the ignition on/off. That's what I was told would damage the engine - not an occasional longish term switch-off.
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Firstly, don't be too hard on yourself. Both you and us have learnt from this episode but more importantly, you weren't hurt. I'm glad you appear to be quite sanguine about it all. Fatigue may well have played a part, but I'll suggest the design of the throttle system "bit you on the bum" because you didn't consider the possibility of a failure.
However, assuming an accurate "History of Flight" ...
I disagree. The root cause appears to be that engine was not "cut" once it had increased to an un-required/in-demanded power setting in excess of what was commanded/required.
Causal Factors were:
1. A throttle spring arrangement that may result in un-commanded excess power being delivered at any time.
2. A throttle (friction) arrangement which allows the above to occur.
3. Continuation of a marginal approach.
Contributory Factors:
1. Too high an approach speed.
2. Too steep approach.
3. Touchdown "deep" into the landing zone.
4. Inappropriate/insufficient contingency planning.
Generic Hazard: System Design
Specific Hazard: Throttle spring arrangement which may allow un-commanded excess power to be delivered at any time.
Generic Hazard: Procedures/Planning
Specific Hazard: Contingency planning, preparation and training for non-standard events.
Generic Hazard: Standards
Specific Hazard: Insufficient understanding and monitoring of approach performance parameters.
As the pilot and "operator" it is now up to you to manage these hazards and I'm sure you will.
Best of luck and "Happy Landings!"
PM
However, assuming an accurate "History of Flight" ...
Mental fatigue was the root cause...
Causal Factors were:
1. A throttle spring arrangement that may result in un-commanded excess power being delivered at any time.
2. A throttle (friction) arrangement which allows the above to occur.
3. Continuation of a marginal approach.
Contributory Factors:
1. Too high an approach speed.
2. Too steep approach.
3. Touchdown "deep" into the landing zone.
4. Inappropriate/insufficient contingency planning.
Generic Hazard: System Design
Specific Hazard: Throttle spring arrangement which may allow un-commanded excess power to be delivered at any time.
Generic Hazard: Procedures/Planning
Specific Hazard: Contingency planning, preparation and training for non-standard events.
Generic Hazard: Standards
Specific Hazard: Insufficient understanding and monitoring of approach performance parameters.
As the pilot and "operator" it is now up to you to manage these hazards and I'm sure you will.
Best of luck and "Happy Landings!"
PM
