Silly Question of the day....
Thread Starter
Silly Question of the day....
Theorhetical scenario.....
Why can't a swept wing jet be belly landed if the engine stops?
Seemed to happen loads in the days of straight winged piston engined days
Have been advised that a swept wing is not the best thing to try and "crash land" in.
This is a serious question.
Lets say the area had tons of flat fields or sand and no population.
Why can't a swept wing jet be belly landed if the engine stops?
Seemed to happen loads in the days of straight winged piston engined days
Have been advised that a swept wing is not the best thing to try and "crash land" in.
This is a serious question.
Lets say the area had tons of flat fields or sand and no population.
Last edited by jimgriff; 20th Dec 2004 at 08:56.
So far as I know, you can - although given a choice and suitable surface most pilots would probably rather have the gear down using the reserve hydraulic system (of-course depending upon what has been determined as most sensible for that aircraft). I recall a case not long ago where a Hawk was dead-sticked into an island somewhere off Scandwegia after the engine failed over the North sea.
I suspect that the reason why in most cases a pilot will elect to eject rather than land in the event of an engine failure is speed. I don't have the numbers to hand, but I'm sure somebody can fill us in - but in general a fast jet will land at speeds at-least 50% greater than a later model piston engined fighter. If you add 50% onto the speed, that adds 125% onto the kinetic energy. This energy has to be dissipated, and you will need considerably more length of flat "field" to land in. But it can be done, and has been done, where conditions are favourable.
G
I suspect that the reason why in most cases a pilot will elect to eject rather than land in the event of an engine failure is speed. I don't have the numbers to hand, but I'm sure somebody can fill us in - but in general a fast jet will land at speeds at-least 50% greater than a later model piston engined fighter. If you add 50% onto the speed, that adds 125% onto the kinetic energy. This energy has to be dissipated, and you will need considerably more length of flat "field" to land in. But it can be done, and has been done, where conditions are favourable.
G
Do a Hover - it avoids G
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jimgriff
Clearly a swept wing jet can be force landed wheels up. The issue is whether it is sensible so to do.
There are several differences between a typical WWII piston fighter and a modern swept wing jet that come into play. If you accept that common sense dictates the need to keep the touchdown speed to a minimum in both cases (which of course means being close to the stall or maximum lift coefficient just prior to touchdown) then thanks to the shallow lift curve slope of a swept wing a very high nose attitude will be needed. This can typically be twice the angle needed with a straight wing – perhaps even more.
This means that when the tail hits the nose really slams down very fast from a great height and that impact can easily break your back. This effect is made even worse by the cockpit being up close to the nose as opposed to behind the engine and near the CG as with a typical piston fighter.
(A friend of mine was taxiing on the hard and had his Harrier nose leg snap off close to the top due to fatigue. The resulting impact when the stub end hit the deck broke his back)
If you do survive this slap down then should a swept wing tip dig in during the ground slide its point of contact is well behind the CG and not far out from the centre line and so the aircraft is more likely to roll into the inverted. Again not good.
To all this add the Genghis numbers and things look pretty dismal. Given the efficiency and reliability of modern ejector seats I suggest you would need a pretty personal reason to try it, rather than punch out.
JF
Clearly a swept wing jet can be force landed wheels up. The issue is whether it is sensible so to do.
There are several differences between a typical WWII piston fighter and a modern swept wing jet that come into play. If you accept that common sense dictates the need to keep the touchdown speed to a minimum in both cases (which of course means being close to the stall or maximum lift coefficient just prior to touchdown) then thanks to the shallow lift curve slope of a swept wing a very high nose attitude will be needed. This can typically be twice the angle needed with a straight wing – perhaps even more.
This means that when the tail hits the nose really slams down very fast from a great height and that impact can easily break your back. This effect is made even worse by the cockpit being up close to the nose as opposed to behind the engine and near the CG as with a typical piston fighter.
(A friend of mine was taxiing on the hard and had his Harrier nose leg snap off close to the top due to fatigue. The resulting impact when the stub end hit the deck broke his back)
If you do survive this slap down then should a swept wing tip dig in during the ground slide its point of contact is well behind the CG and not far out from the centre line and so the aircraft is more likely to roll into the inverted. Again not good.
To all this add the Genghis numbers and things look pretty dismal. Given the efficiency and reliability of modern ejector seats I suggest you would need a pretty personal reason to try it, rather than punch out.
JF
Thread Starter
Thanks Chaps!
Having read and inwardly digested the answer now seems that ejection is the only real viable option in most cases.
Just been thinking about it a bit recently.
Having read and inwardly digested the answer now seems that ejection is the only real viable option in most cases.
Just been thinking about it a bit recently.
Jim,
I've told you before that thinking can be dangerous! Best left to the experts I've found.
I know of at least 1 Tornado F3 and 2 Hawks that were intentionally landed wheels up after undercarriage failures. The were all onto runways and were flown at a faster than normal approach to reduce the nose high attitude that JF discussed. In all cases a few aerials were replaced and the paint touched up and the jets were back flying.
However, the case of "dead-sticking" with no engine would be a whole different kettle of fish... as we have discussed previously.
Regards
T
I've told you before that thinking can be dangerous! Best left to the experts I've found.
I know of at least 1 Tornado F3 and 2 Hawks that were intentionally landed wheels up after undercarriage failures. The were all onto runways and were flown at a faster than normal approach to reduce the nose high attitude that JF discussed. In all cases a few aerials were replaced and the paint touched up and the jets were back flying.
However, the case of "dead-sticking" with no engine would be a whole different kettle of fish... as we have discussed previously.
Regards
T
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I recall a McDD in-house publiction from the late 70s which had details of a USAF (or maybe ANG?) F-4 which had successfully landed wheels-up, with damage to the underwing tanks but no other significant damage.
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Wheels up
we were not allowed to land our swept wing ac wheels up. However, I recall that at least 3 Lightnings were accidently landed wheels up, and they remained upright.
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Tanks for the memory
Or the touch and go "wheels up" that Pedro Condon did at Amberley in a Fantoom.
The drop tanks did a sterling job and we were all very impressed by the sparks. The rear-seater said something rather famous during the touch and go after the burners cut out - but I now forget exactly what that was. It was something to do with "better make the next one a full-stop then" and "but if you want to, we could slip out over the oatswain, jettison the drop-tanks, come back, pretend we never had any and nobody will ever be any the wiser. Whaddya reckon Pedro?"
The Pedro response was reportedly words to the effect: "Shuddup Shorty. Yer only back there to read the bluddy checklist and ya can't even get that right. Bluddy navigators". "Check how much gas is left in those droppers."
"There isn't any."
"Right. I wonder why?"
The drop tanks did a sterling job and we were all very impressed by the sparks. The rear-seater said something rather famous during the touch and go after the burners cut out - but I now forget exactly what that was. It was something to do with "better make the next one a full-stop then" and "but if you want to, we could slip out over the oatswain, jettison the drop-tanks, come back, pretend we never had any and nobody will ever be any the wiser. Whaddya reckon Pedro?"
The Pedro response was reportedly words to the effect: "Shuddup Shorty. Yer only back there to read the bluddy checklist and ya can't even get that right. Bluddy navigators". "Check how much gas is left in those droppers."
"There isn't any."
"Right. I wonder why?"
I vaguely remember seeing a photograph of a Mig-21 that was force landed. Perhaps it was in the Sierra Leone region? Normal finals speed is about 160 kts I think....
It didn't look too bady damaged, I expect the pilot survived.
Gutsy effort, but perhaps his ejection seat didn't work !!
It didn't look too bady damaged, I expect the pilot survived.
Gutsy effort, but perhaps his ejection seat didn't work !!
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There was an incident around 1966/67 when a 56 Sqdn Lightning F3 out of Wattersham did a wheel up crash landing in a field. The aircraft had experienced problems and the Pilot attempted to eject, which failed, this was the first F3 ejection and the canopy release bolts failed to rise correctly and the canopy was not released so the poor chap was trapped.
He successfully carried out a landing in a field (I do not remember if he had any engine power ) but at the end of the landing slide the wing hit a tree/wall, the jolt, jarred the canopy which released, the seat then fired and the poor chap was killed as it was a 90knot minimum speed seat unlike todays zero/zero seats.
There were also other undercarriage problems with the T5, the T 5 had 2 brakeshoot release handles one on the left-hand side near the undercarriage up/down buttons. The other on the right-hand side. There were several incidents of T5s landing and the boots retracting, I witnessed one again at Wattersham in summer 68. 29 Sqdn borrowed a T5 from the OCU at Colt
for the Trappers visits. Touch down was normal, the brake shoot deployed and the left main gear retracted. Both walked away ok. Believe the problem was something along the lines as follows. The left hand brakeshoot handle had about 8 inches of movement, its made of soft iron. As its pulled its magnetic field caused an induced EMF in the U/C ccts located close to the handle. Believe the U/C airspeed switches were set at 145 knots and approaches flow at around 160 knots.
So a defective or miss set switch would not prevent an inadvertent retraction. The initial fix was to operate the brakeshoot handle from the right-hand seat only. So lots of ground crew manage a T5 flight.
He successfully carried out a landing in a field (I do not remember if he had any engine power ) but at the end of the landing slide the wing hit a tree/wall, the jolt, jarred the canopy which released, the seat then fired and the poor chap was killed as it was a 90knot minimum speed seat unlike todays zero/zero seats.
There were also other undercarriage problems with the T5, the T 5 had 2 brakeshoot release handles one on the left-hand side near the undercarriage up/down buttons. The other on the right-hand side. There were several incidents of T5s landing and the boots retracting, I witnessed one again at Wattersham in summer 68. 29 Sqdn borrowed a T5 from the OCU at Colt
for the Trappers visits. Touch down was normal, the brake shoot deployed and the left main gear retracted. Both walked away ok. Believe the problem was something along the lines as follows. The left hand brakeshoot handle had about 8 inches of movement, its made of soft iron. As its pulled its magnetic field caused an induced EMF in the U/C ccts located close to the handle. Believe the U/C airspeed switches were set at 145 knots and approaches flow at around 160 knots.
So a defective or miss set switch would not prevent an inadvertent retraction. The initial fix was to operate the brakeshoot handle from the right-hand seat only. So lots of ground crew manage a T5 flight.
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Nastiest situation is one uc leg stuck up and the other one down. Most jets have an emergency lowering system of one sort or another. Often this is a compressed air bottle which feeds air to the down side of the jacks when a diaphragm is ruptured electrically by the emergency down button. So far so good, but if one leg has failed to come down and pressing the emergency button doesn't lower it then the other one is stuck down and cannot be raised. This rules out a landing on an even keel. Hence the decision to press emergency down may not be straightforward.
With very swept wing jets the advice is to eject if one leg is down and the other up. That said, a Hawk has been successfully landed on one main leg without too much damage. The wing was held off the ground with aileron for a surprisingly long time.
With very swept wing jets the advice is to eject if one leg is down and the other up. That said, a Hawk has been successfully landed on one main leg without too much damage. The wing was held off the ground with aileron for a surprisingly long time.
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........and wasn't there the famous occasion at Farnborough in the 70s when the Saab display pilot landed the 105 trainer wheels up inadvertantly after his display. I think he hurt his back, but not too severely.
Cheers,
mcdhu
Cheers,
mcdhu
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Lots of gee-whiz fighter stuff here but the question remains as there is a whole world of super-critical swept wing aircraft in the business aircraft world. More than one of those has landed gear up and the results vary mostly dependant upon the terrain.
As for the fighter world I believe that the main cause for ejection would stem from the structure of the aircraft being more inclined to disintegrate on impact due to the higher wing loading/approach speeds when engine out. The standard response in most air forces is, if it stops pushing, aim it somewhere safe (time permitting) and get out thus hopefully collecting your silkworm pin.
As for the fighter world I believe that the main cause for ejection would stem from the structure of the aircraft being more inclined to disintegrate on impact due to the higher wing loading/approach speeds when engine out. The standard response in most air forces is, if it stops pushing, aim it somewhere safe (time permitting) and get out thus hopefully collecting your silkworm pin.
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Beleive the old BCARs actually required sufficient fuselage & wing plank thickness that a wheels-up wouldn't start a fire. I remember seeing a mod to add a skid plate to a certain popular Canadian jet after Cranfield had dragged a representative section around (never added to my knowledge).
It's been demo'd a few times in the Biz Jet world - at least once by the HS-125 and once by a GX after one too many gear horn tests. The latter suffered only scratches on the kevlar fairing with the FTE's comment "I thought it was a bit smoother than normal."
It's been demo'd a few times in the Biz Jet world - at least once by the HS-125 and once by a GX after one too many gear horn tests. The latter suffered only scratches on the kevlar fairing with the FTE's comment "I thought it was a bit smoother than normal."
Gentleman Aviator
Farnborough in the 70s when the Saab display pilot landed the 105 trainer wheels up
Red Mud talked about collecting the silk worm pin. In fact it is membership of the "Caterpillar Club", founded during WWII to commemorate all the folks who were saved by using a silk parachute, at the time almost exclusively made by Irvin Ltd. The company these days certainly maintain the database. Ejectees were eligible to join two clubs - The MB Tie Club and the Caterpillar Club, a third, The Porpoise Club was available to those who could claim to have their lives saved by a Beaufort Ltd inflatable product (life jacket or life raft).
However, since about Mk 10 Martin Baker seat, ejectees ar enot eligible for the Caterpillar Club because the parachute used in that and subsequent seats was manufactured by GQ Ltd and not Irvin Ltd.
And BTW this thread has gone a bit off track in talking about wheels up landings as opposed to wheels up engine out landings, two different kettles of fish.
T
PS Got two MB Ties, two Caterpillars (but I lost one) and one Porpoise Club certificate....... wish I didn't
However, since about Mk 10 Martin Baker seat, ejectees ar enot eligible for the Caterpillar Club because the parachute used in that and subsequent seats was manufactured by GQ Ltd and not Irvin Ltd.
And BTW this thread has gone a bit off track in talking about wheels up landings as opposed to wheels up engine out landings, two different kettles of fish.
T
PS Got two MB Ties, two Caterpillars (but I lost one) and one Porpoise Club certificate....... wish I didn't
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Thanks Tarnished for the first-hand knowledge of the pin et al. I also agree that the original question was placed in an "engine out" scenario however, having often practiced both scenarios in the sim (though I do defer to your real-world experience), I have found little difference between rates of descent at the point of touch down. The prime difference being that one is a forced issue with little room for correction while the other can be practiced and reshot if necessary. In any case, here is an excerpt from an recent AIN newsletter...
"On January 13 at about 1715 UTC, a Brazilian-registered Falcon 20 operated by Jet Sul Aero Taxi landed with its gear retracted at Aruba’s Beatrix International Airport. Neither the two pilots nor the sole passenger was injured. While on final approach, the crew reportedly received an onboard alert that the aircraft was flying too low. With its gear still retracted, the jet hit approach and landing lights before touching down on the runway and sliding for about 300 feet before coming to a stop."
"On January 13 at about 1715 UTC, a Brazilian-registered Falcon 20 operated by Jet Sul Aero Taxi landed with its gear retracted at Aruba’s Beatrix International Airport. Neither the two pilots nor the sole passenger was injured. While on final approach, the crew reportedly received an onboard alert that the aircraft was flying too low. With its gear still retracted, the jet hit approach and landing lights before touching down on the runway and sliding for about 300 feet before coming to a stop."