Fatal takeoff accidents
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bjornhall I'm glad to see that a few of us here take a realistic view on perf calculations.
My approach to flying from an 800 Mt grass strip was the same approach I now take flying public transport ops. If the figures didn't add up I wouldn't fly, it's so simple really.
My approach to flying from an 800 Mt grass strip was the same approach I now take flying public transport ops. If the figures didn't add up I wouldn't fly, it's so simple really.
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I think bjornhall is missing the point or perhaps perverting it. If you do not have practical experience of your aircraft under a specific set of circumstances then the margins begin to disappear. Now you need the books.
Why you would want to add 'non-conservative' factors completely escapes me and in no way represents the GASCO/CAA numbers or any other that I have seen. So smokescreen or misdirection.
Certainly add a factor of safety of the nut behind the wheel onto these factors - your own experience should determine what that is. But these accidents happened because none of this happened, the pilots did not calculate performance - they did not even appear to think about it - these people just decided to go for it. And both of these accidents happened under conditions which theoretically should have been good enough (just) for successful takeoffs.
The pilots' performance did not match the test pilots - well there is a surprise. Had they real experience of the aircraft performance they probably would n't have tried it. If they had calculated it they probably would n't have tried it. But they appear to have had neither of these things going for them.
Why you would want to add 'non-conservative' factors completely escapes me and in no way represents the GASCO/CAA numbers or any other that I have seen. So smokescreen or misdirection.
Certainly add a factor of safety of the nut behind the wheel onto these factors - your own experience should determine what that is. But these accidents happened because none of this happened, the pilots did not calculate performance - they did not even appear to think about it - these people just decided to go for it. And both of these accidents happened under conditions which theoretically should have been good enough (just) for successful takeoffs.
The pilots' performance did not match the test pilots - well there is a surprise. Had they real experience of the aircraft performance they probably would n't have tried it. If they had calculated it they probably would n't have tried it. But they appear to have had neither of these things going for them.
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I don't think the safety factors are unfeasible. I think flying from insufficient airstrips is unfeasible. JMHO.
I don't fly anywhere with a runway that's too short according to those sums.
OK, so there are some places I choose not to go that the aircraft might well be physically capable of ...
... but I'm still alive.
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Why you would want to add 'non-conservative' factors completely escapes me and in no way represents the GASCO/CAA numbers or any other that I have seen.
And both of these accidents happened under conditions which theoretically should have been good enough (just) for successful takeoffs.
The pilots' performance did not match the test pilots - well there is a surprise. Had they real experience of the aircraft performance they probably would n't have tried it. If they had calculated it they probably would n't have tried it. But they appear to have had neither of these things going for them.
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But these accidents happened because none of this happened, the pilots did not calculate performance - they did not even appear to think about it - these people just decided to go for it.
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Should there be a factor for the 'age' of the engine? There is probably a peak time for performance when the engine is 'broken' in and after that there is a slow degradation. On our usual 4/6 cylinder Lycomings & Continentals the usual engine performance test is done by using a differential compression check. This check does not take into account cam-shaft wear etc.. The AAIB report about the sad incident of the PA28-140 on the IOW eludes to this problem. It seems to me that any aircraft that is not 'new' will never make manufacturer's book figures. The CAA used to conduct air tests to rate climb performance against the POH but as far as I'm aware never indicated the affect this would have on T/O distances.
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The problem is not that complicated. The AAIB report recommended going back to performance tests - but that is a one off, every three years - and so will not detect camshaft wear, which even they admit generally preceeds faster than that. So the report did not impress me much in that respect.
How about static rpm checking? Every time you open the throttle you have an immediate indication of whether the engine is producing its rated power. Simply checking you are getting the expected static rpm will tell you the engine is OK - or not.
It is one of the things I always check, once the wheels start turning has the engine made its static rpm? Because this is the perfect moment to close the throttle and wonder why not if it hasn't.
Why this did not come out of the report baffles me.
How about static rpm checking? Every time you open the throttle you have an immediate indication of whether the engine is producing its rated power. Simply checking you are getting the expected static rpm will tell you the engine is OK - or not.
It is one of the things I always check, once the wheels start turning has the engine made its static rpm? Because this is the perfect moment to close the throttle and wonder why not if it hasn't.
Why this did not come out of the report baffles me.
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It is one of the things I always check, once the wheels start turning has the engine made its static rpm? Because this is the perfect moment to close the throttle and wonder why not if it hasn't.
A check is a good idea in broad terms, but defining hard limits v go/no-go decisions
NoD
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To give you an example, a Continental C-90, fitted with a 71x52 propeller will deliver around 2100 rpm at start of take-off. Only a very small increase in the rpm will occur as a result of headwind; groundspeed is not relevant as the check is made as you initially open the throttle - and tailwind won't apply on a limiting take-off, surely?
I think gasax makes a very valid point.
JD
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Certainly spend some money with an engineer. An engine should be able to make very close to full rated power for its TBO. If there is any significant degradation something is actually on its way to failing! Engines are very simple things and lack of power is going to be due to a blockage in airflow (i.e. valves not fully opening), lack of compression (valves not closing or significant ring/cylinder issues), lack of fuel flow, or lack/low/wrong time spark - all of these are due to mechanical problems that are probably going to get worse reasonably quickly.
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Max RPM is one of my first checks when I open the throttle. It does not vary by more than 50rpm from the 5400 I set when I built the aircraft. If it did, I would abort immediately and investigate.
Just to be clear, it is the CAA safety factors which are regularly ignored and which would impact a lot of the short runway flying that goes on. The system gasax explains is how most people do it. Interestingly, it is generally not the based aircraft which hit the hedge, but the visitors.
Rod1
Just to be clear, it is the CAA safety factors which are regularly ignored and which would impact a lot of the short runway flying that goes on. The system gasax explains is how most people do it. Interestingly, it is generally not the based aircraft which hit the hedge, but the visitors.
Rod1
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OK - so your engine doesn't make the static RPM what do you do? Spend £10,000 getting it replaced!
Are you insane? Do you have a deathwish? If not then anyone with more than 2 braincells to rub together will go "Hmm something not right here, lets stop."
All takeoffs should be assumed as to be rejected until proven otherwise.
You stop and get the people in oily overalls to have a look. What you don't do is continue the takeoff!
I use a basic rule of if I haven't reached 70% of flying speed by 50% of runway available, then I stop.
Taildraggers are a bit different as you can't just stamp on the brakes. Well you can and you will stop quickly, but you might have a bit of a problem with using the aircraft again.
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residents are safer . . . . . . . .
Interestingly, it is generally not the based aircraft which hit the hedge, but the visitors
As regards the accident at Shotteswell, how many of the people posting have flown in there? I did once, and I looked at the short runway and thought "downhill only, on a good day", and that was with 200 hours experience in the aircraft operating off a 600 yard strip.
I'm afraid that I agree with the comment about "lunatic". He took off uphill in an aircraft type he hardy knew, with a huge hedge at the far end (which he had taxied past but could not see at the start of his take-off). The other matters of airmanship which the AAIB mentioned as fact without comment make you wonder if you would have rented your own aircraft to him!
I'm afraid that I agree with the comment about "lunatic". He took off uphill in an aircraft type he hardy knew, with a huge hedge at the far end (which he had taxied past but could not see at the start of his take-off). The other matters of airmanship which the AAIB mentioned as fact without comment make you wonder if you would have rented your own aircraft to him!
