Catastrophic structural failure
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This sort of failure mode, either catastrophic physical collapse
or loss of key control surfaces does happen and is a significant
contributor to fatal accidents in light aircraft.
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Well Andrewc, you're right it does happen, but you're wrong in stating that it is a significant contributor to fatal accidents.
Structural failure is virtually the least common cause of fatal accidents.
Start with all the pilot caused varieties, continued flight into IFR, landing and takeoff incidents, mechanical (i.e. engine failure, running out of fuel etc, etc.). And then you get to structural failure - so long as you have already captured pilot error over-stressing the airframe due to un-approved aerobatics, loss of control, dis-orientation.
There is no doubt the ballistic parachute gives a great sense of safey - but it will never significantly reduce the fatal accident rate.
This sort of failure mode, either catastrophic physical collapse
or loss of key control surfaces does happen and is a significant
contributor to fatal accidents in light aircraft.
===========================================
Well Andrewc, you're right it does happen, but you're wrong in stating that it is a significant contributor to fatal accidents.
Structural failure is virtually the least common cause of fatal accidents.
Start with all the pilot caused varieties, continued flight into IFR, landing and takeoff incidents, mechanical (i.e. engine failure, running out of fuel etc, etc.). And then you get to structural failure - so long as you have already captured pilot error over-stressing the airframe due to un-approved aerobatics, loss of control, dis-orientation.
There is no doubt the ballistic parachute gives a great sense of safey - but it will never significantly reduce the fatal accident rate.
Do a Hover - it avoids G
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Hersham Boy
As it happens I was at Coventry, watched the Ryan take-off, but looked away left just before the accident. Starting in 1951 I have watched 10 aircraft crash at airshows. Nine were classic pilot pigs and one you could argue about.
But in the context of your post (and NOT this very sad accident) I would like to raise the issue of walk around checks as I think they are not always done properly.
My experience of watching many pilots do such checks leads me to feel they are often a token ritual banging, thumping waggling set of actions, rather than a serious inspection of the aeroplane. Just one example will serve to illustrate the point I am making, namely what we can do to check an aileron.
At the very least we want to carefully stand in front of it, then using two hands, gently and with feeling, move it over its full range of travel while concentrating on assessing whether there is any lack of smoothness in the friction forces or small noise that might indicate something rubbing. Is there a nice smooth stop at full deflection both ways? Has the surface any abnormal end play? A quick grab and waggle as you pass by will not tell you these things. Depending on the type, what can you see of the condition of the hinges and wire locking of any associated bolts? What about evidence of lubrication or corrosion? Is the bonding wire in place? If there are bolts holding on a mass balance are they properly locked? If there are drain holes in the surface are they clear? What about backlash in the circuit (if you have a passenger or crew member ask them to hold the other one central while you carefully, again with feeling, try and detect free play on your side) I could go on but I am sure you get my point.
Of course if you have done several flights that day, your inspection can be much reduced. But not before the first flight. It is your neck, so do what you reasonably can to look after it.
What I like to see is a pilot who from different angles includes standing still and LOOKING at the aircraft. Really studying it.
Sorry I don't mean to rant
John
As it happens I was at Coventry, watched the Ryan take-off, but looked away left just before the accident. Starting in 1951 I have watched 10 aircraft crash at airshows. Nine were classic pilot pigs and one you could argue about.
But in the context of your post (and NOT this very sad accident) I would like to raise the issue of walk around checks as I think they are not always done properly.
My experience of watching many pilots do such checks leads me to feel they are often a token ritual banging, thumping waggling set of actions, rather than a serious inspection of the aeroplane. Just one example will serve to illustrate the point I am making, namely what we can do to check an aileron.
At the very least we want to carefully stand in front of it, then using two hands, gently and with feeling, move it over its full range of travel while concentrating on assessing whether there is any lack of smoothness in the friction forces or small noise that might indicate something rubbing. Is there a nice smooth stop at full deflection both ways? Has the surface any abnormal end play? A quick grab and waggle as you pass by will not tell you these things. Depending on the type, what can you see of the condition of the hinges and wire locking of any associated bolts? What about evidence of lubrication or corrosion? Is the bonding wire in place? If there are bolts holding on a mass balance are they properly locked? If there are drain holes in the surface are they clear? What about backlash in the circuit (if you have a passenger or crew member ask them to hold the other one central while you carefully, again with feeling, try and detect free play on your side) I could go on but I am sure you get my point.
Of course if you have done several flights that day, your inspection can be much reduced. But not before the first flight. It is your neck, so do what you reasonably can to look after it.
What I like to see is a pilot who from different angles includes standing still and LOOKING at the aircraft. Really studying it.
Sorry I don't mean to rant
John
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OK - I'll promise to try a DR400 
This many users can't be wrong!
I understand your point, John - early on in my training I was caught out leaving the oil filler cover unlatched on a C152 because it was freezing cold and I was in a bit of a hurry to get warm. It flipped open in flight. As it sits edge-on to the airflow no harm was done but I felt like a right plank and learned to slow-down and be more thorough!
But my concern is not so much with my checking of the a/c but whether I would actually be able to spot, say, the fractured spar that was the result of the Robin striking the hay bale in the AAIB report earlier in the thread. It is pure conjecture, of course, but perhaps that pilot made a thorough check of the a/c following the incident and satisfied himself it was undamaged?
It's a rhetorical question, of course. There's no way you could spot a fractured spar (or similar) on a walkround and I understand the statistics for this kind of incident are very low. It's just this kind of possibility, however remote, that would keep me flying tank-like spamcans!
I must be getting risk-averse in my old age
Hersh
This many users can't be wrong!I understand your point, John - early on in my training I was caught out leaving the oil filler cover unlatched on a C152 because it was freezing cold and I was in a bit of a hurry to get warm. It flipped open in flight. As it sits edge-on to the airflow no harm was done but I felt like a right plank and learned to slow-down and be more thorough!
But my concern is not so much with my checking of the a/c but whether I would actually be able to spot, say, the fractured spar that was the result of the Robin striking the hay bale in the AAIB report earlier in the thread. It is pure conjecture, of course, but perhaps that pilot made a thorough check of the a/c following the incident and satisfied himself it was undamaged?
It's a rhetorical question, of course. There's no way you could spot a fractured spar (or similar) on a walkround and I understand the statistics for this kind of incident are very low. It's just this kind of possibility, however remote, that would keep me flying tank-like spamcans!
I must be getting risk-averse in my old age
Hersh
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People are also unaware of the amount of damage that can be caused to a spamcan by a seemingly minor scrape.
Noth that the pilot of this PA28 elected to fly it, unaware that he had damaged the wing spar attachments.
The wing is inherently strong and forms a long lever. If you apply pressure to one end of it, spread over an area, you are just as likely to cause serious and invisible damage to the root attachments with little or no visible surface damage at the point of impact if it is made of metal as if it is made of wood.
In the case of the PA28 above he hit a post. Localised pressure meant that surface damage was visible. If it had been something soft like a hay bale he would have caused just as much damage to the spar attachments but less visible surface damage because the pressure would have been applied over a larger area.
Mike
Noth that the pilot of this PA28 elected to fly it, unaware that he had damaged the wing spar attachments.
The wing is inherently strong and forms a long lever. If you apply pressure to one end of it, spread over an area, you are just as likely to cause serious and invisible damage to the root attachments with little or no visible surface damage at the point of impact if it is made of metal as if it is made of wood.
In the case of the PA28 above he hit a post. Localised pressure meant that surface damage was visible. If it had been something soft like a hay bale he would have caused just as much damage to the spar attachments but less visible surface damage because the pressure would have been applied over a larger area.
Mike
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Hersh -
I don't know about that. I'll admit to the possibility that some forms of internal damage may leave no external sign, but there are quite a few ways such damage might reveal itself, albeit subtle. I have always made a practice of carrying out JF's advice about standing back and looking at the aeroplane from a reasonable distance, from different angles. Does the dihedral look right? From square on the nose, does the tailplane make a right angle with the fin? Do the tips of the tailplane tappear to touch the visual surface of the wings in the right place? Is there any unusual washout or washin? Closer in, perhaps using reflections off the skin, are there any signs of stress such as faint wrinkles running diagonally across metal or fabric panels? Are there any rivets or stiches which are starting to pull or come loose? If you push up carefully on the wing tip, does the wing take up the strain evenly, and are there any sounds you wouldn't expect? Do the doors and removable access panels fit in the same way they always have, or is there a bit of a struggle to get latches / fasteners home? Are hinges rubbing or binding? On biplanes of course you also have the condition and tensions of the rigging wires to look at.All these could be clues to something having changed inside the structure.
There's no way you could spot a fractured spar (or similar) on a walkround
I'm with JF - much can be seen on a pre-flight, and much of it regularly isn't. I recall a while ago somebody flying an aircraft to me for an air test, insisting on doing my own pre-flight despite his having just landed it and finding a dozen or so serious faults.
Having said that, are pilots properly trained to see these faults? I had an interesting conversation with Whirlybird recently where she recounted being taught during her AHI course how to do an A-check, but was taught it by a LAME, not a pilot. That may arguably be a practice that should be spread.
And yes, before now I've flown somewhere for a meeting, walked back to my aircraft with another Engineer before departing, who has idly pointed out faults on my own aircraft that I'd missed on my pre-flight. Embarrassing but good sport. I know of a club where finding a fault on somebody else's private aircraft earns you a pint - it's in the club rules, and the standard of aircraft there is sparkling !
G
Having said that, are pilots properly trained to see these faults? I had an interesting conversation with Whirlybird recently where she recounted being taught during her AHI course how to do an A-check, but was taught it by a LAME, not a pilot. That may arguably be a practice that should be spread.
And yes, before now I've flown somewhere for a meeting, walked back to my aircraft with another Engineer before departing, who has idly pointed out faults on my own aircraft that I'd missed on my pre-flight. Embarrassing but good sport. I know of a club where finding a fault on somebody else's private aircraft earns you a pint - it's in the club rules, and the standard of aircraft there is sparkling !
G
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I'm well-willing to have an engineer (or other well-informed personage) show me a proper A Check (correct terminology?)
Genghis - I don't think you're East Surrey? Anyone who's local to EGKR who is willing to show the ropes would be welcomed with a smile and (a) subsequent pint(s).
Feel free to post or PM! Cheers to any and all willing to help
Hersh
Genghis - I don't think you're East Surrey? Anyone who's local to EGKR who is willing to show the ropes would be welcomed with a smile and (a) subsequent pint(s).
Feel free to post or PM! Cheers to any and all willing to help
Hersh
'Fraid not, but in this context I think you want a LAME familiar with / rated on the type, rather than a more academic gingerbeer like m'self. I know the types I fly and work on on-principle and out of self preservation, but I'm not licensed in that context.
I think the correct terminology is actually "Check A", but many people call it a DI (Daily Inspection).
G
I think the correct terminology is actually "Check A", but many people call it a DI (Daily Inspection).
G
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What I like to see is a pilot who from different angles includes standing still and LOOKING at the aircraft. Really studying it.
I learnt this by not following the above advice, before flying a Slingsby T67. I gave the undercarriage a cursory inspection, and it looked normal on both sides. However, it wasn't. The right side was damaged by an earlier heavy landing, which could be clearly seen when looking at both sides from a distance.
Fortunately the damage was so severe that the aeroplane pulled to one side when taxying, so I abandoned the trip before takeoff. It turned out that the wing had been badly damaged as well, but this was not visible externally.
If I had flown, there would inevitably have been an accident.
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quote:
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There's no way you could spot a fractured spar (or similar) on a walkround
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This actually a lot easier on a fabric covered aeroplane than on a metal one - another very good reason for flying a Robin. During the walkround, drum your fingers on the fabric between each pair of adjacent ribs and listen. Even if the skin isn't wrinkled, any lack of tautness will be audible as a much duller sound. You should certainly be able to spot a damaged rib by this method.
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There's no way you could spot a fractured spar (or similar) on a walkround
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This actually a lot easier on a fabric covered aeroplane than on a metal one - another very good reason for flying a Robin. During the walkround, drum your fingers on the fabric between each pair of adjacent ribs and listen. Even if the skin isn't wrinkled, any lack of tautness will be audible as a much duller sound. You should certainly be able to spot a damaged rib by this method.
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There have been lots of incidences of structural failure after loss of control in IMC or very severe turbulence, but structural failures (this weekend's tragedy apart, where we don't yet know the cause) where the aeroplane has not exceeded its design limts are (AFAIK) just about non existant. Anyone know of any?
