A comment on ensuring landing gear down if forced landing a retractable gear aircraft
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If the bleedin' donk has thrown in the towel then the whole shebang belongs to the insurance company. My concern at that point becomes me; if I get out ok then so will the pax. Every decision from the point of silence is governed by that one thought.
I have to admit that I spent a lot of hours in C210s' flying out of Alice Springs and many a long flight was spent going "what if it all goes silent?", "where would I go?", "wheels up or down?". As to the latter it would mostly have been wheels up; the ground may be as hard as bu##ery out there but the rocks would be the killer. The only possible exception would be if there was a half-way decent road and even then it would be touch or go decision.
JT, I understand where you are coming from but the collapse may not be gradual and there may be significant more damage caused to the fuselage in the event of, say one undercarriage leg been broken off, or worse snapped in half.
I have to admit that I spent a lot of hours in C210s' flying out of Alice Springs and many a long flight was spent going "what if it all goes silent?", "where would I go?", "wheels up or down?". As to the latter it would mostly have been wheels up; the ground may be as hard as bu##ery out there but the rocks would be the killer. The only possible exception would be if there was a half-way decent road and even then it would be touch or go decision.
JT, I understand where you are coming from but the collapse may not be gradual and there may be significant more damage caused to the fuselage in the event of, say one undercarriage leg been broken off, or worse snapped in half.
Last edited by PLovett; 17th May 2013 at 12:12.
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Of course, there are no guarantees and the Monday morning quarterbacking may not be kind.
However, the aims in the heat of the moment remain as per Crashes 101 -
(a) maintaining survival volume
(b) reducing peak decelerations
I have my views based on general vehicle engineering and aircraft seat testing background, you are entitled to yours and they are respected.
However, the aims in the heat of the moment remain as per Crashes 101 -
(a) maintaining survival volume
(b) reducing peak decelerations
I have my views based on general vehicle engineering and aircraft seat testing background, you are entitled to yours and they are respected.
Of course, wheels up or wheels down some impacts will be unsurvivable. What you should be doing is loading the dice in your favour.
Me ? Hang the aircraft .. it's wheels down just about every time and fly the machine as far into the prang as is practicable with a view to delaying hitting anything hard until the speed is right down there in the low numbers
Me ? Hang the aircraft .. it's wheels down just about every time and fly the machine as far into the prang as is practicable with a view to delaying hitting anything hard until the speed is right down there in the low numbers
Whether landing on a runway or an unprepared surface, the principle of energy absorption by the landing gear is the same.
Readers may recall from ten years ago, the Duchess that crashed at Camden following a simulated engine failure shortly after lift off. The student (10,000 hours) selected gear up and at 100 feet the instructor cut one mixture lever. With the prop windmilling because the instructor had not set zero thrust, the aircraft was unable to climb and after clipping a tree top, belly landed into rising ground. It went through a wire fence and both occupants were uninjured. The right wing then hit an iron girder which split the wing and fuel was ignited. The two pilots evacuated the aircraft but were caught by the fire. One pilot survived with severe burns while the other pilot died of burns.
if the landing gear had been down when the Duchess hit the rising ground, the wing may have been high enough off the surface to clear the obstruction. Of course, that is a what- if situation, but it seems to me there are more advantages to landing gear down than on its belly gear up.
I once saw the tragic results to a pilot who lost an engine in his trike and forced landed on rocky ground. Being a trike, the pilot's seat was like that of a deck chair only inches of the ground with the inevitable result the pilot received severe spinal injuries because of lack of energy absorbing space between seat and ground.
Going back to the original post, where the USAF had Sabre fighters that had landed wheels up and caused pilot spinal injuries. The lesson was soon learnt that energy absorption was vital to minimise spinal injuries and so the advice to land wheels down on unprepared surfaces was made standard forced landing procedure.
That information is as valid now as it was sixty years ago.
Last edited by Centaurus; 17th May 2013 at 15:15.
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Aviation is full of myths.
Jaba dislikes the one about ROP and "over square"'
I dislike how so any " know" the right way to force land when neither they or their instructors ( however long ago) have done one!
Jaba dislikes the one about ROP and "over square"'
I dislike how so any " know" the right way to force land when neither they or their instructors ( however long ago) have done one!
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If not on the bitumen, you might as well leave it up ...
I tried to think of a nice way to say it, but I couldn't. Sorry.
I know we are talking about 'Retractable Gear' aircraft here, but google the images of the VH-JGR crash, (fixed gear) where the pilot barely survived the impact, and then try to tell me that gear didn't absorb a whole lot of the impact forces, which probably was the difference between life and death.
Trent
there are 2 weaknesses of your argument:
1. JGR did not hit the ground in a controlled glide. It reads more like a stall / spin impact.
2. I don't think the behaviour (on impact) of the Wittman style fixed undercarriage cessna can be used to model how the structure of a retractable undercarriage performs.
there are 2 weaknesses of your argument:
1. JGR did not hit the ground in a controlled glide. It reads more like a stall / spin impact.
2. I don't think the behaviour (on impact) of the Wittman style fixed undercarriage cessna can be used to model how the structure of a retractable undercarriage performs.
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OA, controlled glide/stall spin, has not been bought up in this discussion till now.
I made the reference to JGR only to show how much energy the gear absorbed to bend like that before the hull impacted.
The discussion so far is whether to have the wheels out to absorb impact energy before the hull absorbs all the energy. The difference between a 172 fixed gear and a 182RG gear in that circumstance would be negligible.
I refer you back to my first post to FTDK when I indicated preconceived actions may not be as good as making the call as and when required.
CTR says 'gear-up' unless it is bitumen. My personal opinion is, that is bullsh!t of the first order.
CTR, I grew up on outback cattle stations flying 182 and 182RG's. Your "premadonna" label bothers me not.
JT has given a most enlightening discourse and I have to admit I agree with him.
I made the reference to JGR only to show how much energy the gear absorbed to bend like that before the hull impacted.
The discussion so far is whether to have the wheels out to absorb impact energy before the hull absorbs all the energy. The difference between a 172 fixed gear and a 182RG gear in that circumstance would be negligible.
I refer you back to my first post to FTDK when I indicated preconceived actions may not be as good as making the call as and when required.
CTR says 'gear-up' unless it is bitumen. My personal opinion is, that is bullsh!t of the first order.
CTR, I grew up on outback cattle stations flying 182 and 182RG's. Your "premadonna" label bothers me not.
JT has given a most enlightening discourse and I have to admit I agree with him.
Last edited by Trent 972; 18th May 2013 at 01:41. Reason: formatting
Slight 'drift'.....
Re the JGR ATSB report, did anyone notice the following..
'The pilot was the only person on board and suffered severe injuries as a result of the accident and was airlifted to hospital.'
Followed by...
Highest injury level: Minor
And further on...
Damage to aircraft: Unknown
From the photos on google, I would have said 'aircraft destroyed'...
Que..??
Re the JGR ATSB report, did anyone notice the following..
'The pilot was the only person on board and suffered severe injuries as a result of the accident and was airlifted to hospital.'
Followed by...
Highest injury level: Minor
And further on...
Damage to aircraft: Unknown
From the photos on google, I would have said 'aircraft destroyed'...
Que..??
Last edited by Ex FSO GRIFFO; 18th May 2013 at 02:01.
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A photo, they say, speaks a thousand words.
The P-51 prototype following a landing in a freshly ploughed field as a result of an engine failure. The test pilot was stuck in the cockpit until rescuers were able to dig him out. Note the wheels, seemingly undamaged.
Perhaps there may have been a reason WWII crews force landed their P-51, P-47, Spitfires, Lancasters etc etc gear up. Both the P-51 and Spitfire manuals dictate gear up.
The P-51 prototype following a landing in a freshly ploughed field as a result of an engine failure. The test pilot was stuck in the cockpit until rescuers were able to dig him out. Note the wheels, seemingly undamaged.
Perhaps there may have been a reason WWII crews force landed their P-51, P-47, Spitfires, Lancasters etc etc gear up. Both the P-51 and Spitfire manuals dictate gear up.
I made the reference to JGR only to show how much energy the gear absorbed to bend like that before the hull impacted.
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Its not the undercart that did the energy absorbing
The gear legs are bent up like that because they became frightened just prior to impact.
I continue to learn...
Last edited by Trent 972; 18th May 2013 at 02:52. Reason: add quote
Yeah, but the gear bent after initial impact.
If it was a spin there would have been a lateral force on impact that undercat is not stressed for (due to the yaw). The damage to the gear is collateral damage after initial impact, not (as you suggest) part of the energy absorption of the impact. Get a model and set it on the table 20 deg nose down with 60 deg bank.
Where are the wings in the photo? That is what took the bulk of the impact. The wing strut has pulled out from the fueselage attach point. Who knows what collateral damage that caused to the monocoque structure adjacent to the undercart.
The angle of the engine is testament to the nose down attitude that almost certainly saw the engine contacting before the undercart. Moving a 100 kg plus lump of metal and bending / breaking the engine mount or firewall absorbs large lumps of energy.
Aeroplanes are frankly not very crashworthy structures. If you have any doubt, have a close look at how your seatbelts attach. Cars use a 7/16 inch grade 10 (from memory) bolt. Aircraft use something like a 1/4 inch AN bolt. AN bolts are about Grade 8 strength (a little stronger). This bolt typically attaches to CrMo sheet brackets that are often cherry riveted to a non-structural aluminium panel. If you hit the ground in an uncontrolled descent, you're in pretty serious trouble and the gear is not going to help, wherever it is.
Conversely, if you hit the ground in a controlled glide (eg forced landing), then the gear is going to help a lot and the debate about whether or not its tucked up in the belly is worthwhile. You hope / expect to walk away from these.
If it was a spin there would have been a lateral force on impact that undercat is not stressed for (due to the yaw). The damage to the gear is collateral damage after initial impact, not (as you suggest) part of the energy absorption of the impact. Get a model and set it on the table 20 deg nose down with 60 deg bank.
Where are the wings in the photo? That is what took the bulk of the impact. The wing strut has pulled out from the fueselage attach point. Who knows what collateral damage that caused to the monocoque structure adjacent to the undercart.
The angle of the engine is testament to the nose down attitude that almost certainly saw the engine contacting before the undercart. Moving a 100 kg plus lump of metal and bending / breaking the engine mount or firewall absorbs large lumps of energy.
Aeroplanes are frankly not very crashworthy structures. If you have any doubt, have a close look at how your seatbelts attach. Cars use a 7/16 inch grade 10 (from memory) bolt. Aircraft use something like a 1/4 inch AN bolt. AN bolts are about Grade 8 strength (a little stronger). This bolt typically attaches to CrMo sheet brackets that are often cherry riveted to a non-structural aluminium panel. If you hit the ground in an uncontrolled descent, you're in pretty serious trouble and the gear is not going to help, wherever it is.
Conversely, if you hit the ground in a controlled glide (eg forced landing), then the gear is going to help a lot and the debate about whether or not its tucked up in the belly is worthwhile. You hope / expect to walk away from these.
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Kelly
You need to make yourself known to me by PM
I suspect I can narrow you down to a list of names
Tankengine
Ahhh yes but the myths are easily busted with data.
Same applies here
You need to make yourself known to me by PM
I suspect I can narrow you down to a list of names
Tankengine
Aviation is full of myths.
Jaba dislikes the one about ROP and "over square"'
I dislike how so any " know" the right way to force land when neither they or their instructors ( however long ago) have done one!
Jaba dislikes the one about ROP and "over square"'
I dislike how so any " know" the right way to force land when neither they or their instructors ( however long ago) have done one!
Same applies here
Moderator
This thread is rather valuable for the to and fro commentary.
If I may add some additional thoughts ..
(a) If not, well, its not going to worry the pilot.
If the pilot/others are dead, then the crash was unsurvivable for whatever reasons. Sad for those left behind but, as you observe, not a problem thereafter for the pilot.
If the pilot/others experience no injuries (for instance, my only prang, years ago in a Bocian .. also my first glider ride ... left the unit in tatters and small bits of structure after we collected a fence post during an outlanding out at Penrith .. that was another story ... but, after both of us shook the remains from around us, we found ourselves without a scratch, bruise or other injury ... very embarrassing back at RIC that night, though as the glider had only just come out of overhaul) ... then, no problems.
HOWEVER, if the occupants suffer significant but non-lethal injuries, it is a whole different ball game. Every bit of advantage the pilot can build in to the outcome may just keep you out of a wheelchair or worse.
(b) Going A over T is a real risk if you don't have a great knowledge of the surface in question
Absolutely valid consideration. But only one aspect of the risk decision process. The aim ought not only to be avoiding ending up on your back but minimising the overall risk of injury .. horses for courses with the Type and circumstances on the day.
(c) Both the P-51 and Spitfire manuals dictate gear up.
As with all matters one would be factoring in the OEM's guidance.
A superstructure cockpit without surrounding crushable structure to help out in the case of a rollover together with a reasonable lower keel structure would be a good reason to favour gear up. Again, horses for courses. (Could be a good after dinner topic for discussion, Brian ?)
(d) Yeah, but the gear bent after initial impact.
The initial sequence doesn't matter all that much. The start of the prang is whatever the pilot makes of the final approach and touchdown. From there on, the basics of Crashes 101 are all that is important. Whether it's the wheels which bend and break .. or the wings ... or anything other than the occupants ... is good. Same philosophy applies with a paddock full of trees ... hit them with the wings, not the nose ...
(e) Aeroplanes are frankly not very crashworthy structures
As with most things ... it depends on what you might be expecting ...
The basic Certification strategy is that aircraft survivability is to do with an off-airport landing on a smooth, firm and generally suitable surface to permit a relatively gentle deceleration to a stop. If you run into something substantial, all bets are off.
Indeed, the most graphic picture I can recall is of the cliff face into which a B1B impacted at low level high speed flight conditions ... a black smudge and nothing much else that I can recall distinguishing.
As a consequence of the basic requirements, the early design standards envisaged maximum decelerations in the order of 6G. This was later upped to 9G. Later still, when the use of dynamic sled tests in the motor vehicle industry demonstrated that the very much higher peak loadings could be tolerated without horrendous design and manufacturing cost, the aircraft Standards adopted the motor vehicle Standards albeit with a few odds and ends added on.
Your motor car looks to full on impacts and the present Standards should serve you well up to, say, 50 to 60 kph. The aircraft can't quite aim for that sort of impact but, with the present dynamic standard seats, you are served well in most reasonable off airport prangs ... PROVIDING that you don't hit big and/or hard things.
Crashes 101 still reigns supreme.
(f) This bolt typically attaches to CrMo sheet brackets that are often cherry riveted to a non-structural aluminium panel.
Designs may vary but, if they are well thought out, things are a lot better than you might infer from the above comment.
I recall a cargo MU2 prang many years ago at Bargo or somewhere nearby. The cargo restraint system was of my approved design.
Barry S, the lead investigator, rang me at home to let me know that the aircraft had disintegrated around my cargo restraint provisions .. a bit of exaggeration on his part, no doubt, but the point remains, it is not very difficult to engineer an effective and progressively deforming restraint anchorage in an aircraft structure ...
Crashes 101 still remains supreme.
Only the detail on the day varies ...
If I may add some additional thoughts ..
(a) If not, well, its not going to worry the pilot.
If the pilot/others are dead, then the crash was unsurvivable for whatever reasons. Sad for those left behind but, as you observe, not a problem thereafter for the pilot.
If the pilot/others experience no injuries (for instance, my only prang, years ago in a Bocian .. also my first glider ride ... left the unit in tatters and small bits of structure after we collected a fence post during an outlanding out at Penrith .. that was another story ... but, after both of us shook the remains from around us, we found ourselves without a scratch, bruise or other injury ... very embarrassing back at RIC that night, though as the glider had only just come out of overhaul) ... then, no problems.
HOWEVER, if the occupants suffer significant but non-lethal injuries, it is a whole different ball game. Every bit of advantage the pilot can build in to the outcome may just keep you out of a wheelchair or worse.
(b) Going A over T is a real risk if you don't have a great knowledge of the surface in question
Absolutely valid consideration. But only one aspect of the risk decision process. The aim ought not only to be avoiding ending up on your back but minimising the overall risk of injury .. horses for courses with the Type and circumstances on the day.
(c) Both the P-51 and Spitfire manuals dictate gear up.
As with all matters one would be factoring in the OEM's guidance.
A superstructure cockpit without surrounding crushable structure to help out in the case of a rollover together with a reasonable lower keel structure would be a good reason to favour gear up. Again, horses for courses. (Could be a good after dinner topic for discussion, Brian ?)
(d) Yeah, but the gear bent after initial impact.
The initial sequence doesn't matter all that much. The start of the prang is whatever the pilot makes of the final approach and touchdown. From there on, the basics of Crashes 101 are all that is important. Whether it's the wheels which bend and break .. or the wings ... or anything other than the occupants ... is good. Same philosophy applies with a paddock full of trees ... hit them with the wings, not the nose ...
(e) Aeroplanes are frankly not very crashworthy structures
As with most things ... it depends on what you might be expecting ...
The basic Certification strategy is that aircraft survivability is to do with an off-airport landing on a smooth, firm and generally suitable surface to permit a relatively gentle deceleration to a stop. If you run into something substantial, all bets are off.
Indeed, the most graphic picture I can recall is of the cliff face into which a B1B impacted at low level high speed flight conditions ... a black smudge and nothing much else that I can recall distinguishing.
As a consequence of the basic requirements, the early design standards envisaged maximum decelerations in the order of 6G. This was later upped to 9G. Later still, when the use of dynamic sled tests in the motor vehicle industry demonstrated that the very much higher peak loadings could be tolerated without horrendous design and manufacturing cost, the aircraft Standards adopted the motor vehicle Standards albeit with a few odds and ends added on.
Your motor car looks to full on impacts and the present Standards should serve you well up to, say, 50 to 60 kph. The aircraft can't quite aim for that sort of impact but, with the present dynamic standard seats, you are served well in most reasonable off airport prangs ... PROVIDING that you don't hit big and/or hard things.
Crashes 101 still reigns supreme.
(f) This bolt typically attaches to CrMo sheet brackets that are often cherry riveted to a non-structural aluminium panel.
Designs may vary but, if they are well thought out, things are a lot better than you might infer from the above comment.
I recall a cargo MU2 prang many years ago at Bargo or somewhere nearby. The cargo restraint system was of my approved design.
Barry S, the lead investigator, rang me at home to let me know that the aircraft had disintegrated around my cargo restraint provisions .. a bit of exaggeration on his part, no doubt, but the point remains, it is not very difficult to engineer an effective and progressively deforming restraint anchorage in an aircraft structure ...
Crashes 101 still remains supreme.
Only the detail on the day varies ...
"JT" you add valuable reading here
At the end of the day it's one of three things that will end a humans life as far as A/C accidents are concerned, well any machine mankind happens to be in during a crash sequence. One is blunt force trauma, usually the most prolific in an accident sequence. Secondly lack of o2 to the brain associated with fire within the cabin cell. Third is & this can be associated with the first I mentioned here & that's sudden deceleration, such high forces as has been mentioned here already can & usually dislodges the main organs, mainly the heart & spleen, both will take you out pretty quick due bleeding out.
All not very pleasant I know but if your faced with the unthinkable possible high impact forces then all one can do is lesson the impact by way of letting the airframe absorb as much as possible.
Unless it's looking obvious that landing wheels up is the best controlled way I believe & this is just my opinion that land with everything hanging out.
Having worked with the RFDS for many years I saw way too much of the results of blunt force trauma, enough to last me 4ever sadly!
Wmk2
At the end of the day it's one of three things that will end a humans life as far as A/C accidents are concerned, well any machine mankind happens to be in during a crash sequence. One is blunt force trauma, usually the most prolific in an accident sequence. Secondly lack of o2 to the brain associated with fire within the cabin cell. Third is & this can be associated with the first I mentioned here & that's sudden deceleration, such high forces as has been mentioned here already can & usually dislodges the main organs, mainly the heart & spleen, both will take you out pretty quick due bleeding out.
All not very pleasant I know but if your faced with the unthinkable possible high impact forces then all one can do is lesson the impact by way of letting the airframe absorb as much as possible.
Unless it's looking obvious that landing wheels up is the best controlled way I believe & this is just my opinion that land with everything hanging out.
Having worked with the RFDS for many years I saw way too much of the results of blunt force trauma, enough to last me 4ever sadly!
Wmk2