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What If The Horizontal Stabilizer Was Lost?  
User currently offlineFlexo From St. Helena, joined Mar 2007, 406 posts, RR: 0
Posted (7 years 1 month 2 weeks 4 days 20 hours ago) and read 8560 times:

Ok, I found myself wondering what would happen if you were to lose the horizontal stabilizer in mid flight (i.e. seperated from the fuselage).
Obviously you would be in bad trouble, but would the nose go up or down? Intuitively I'd say id would go down before going out of control, but then again the horizontal stabilizer probably produces some lift so if it was lost it seems like the nose would go up instead.

Any educated guesses?

Also: Would there be any chance of keeping the aircraft under control after the loss of such an essential part?

84 replies: All unread, showing first 25:
 
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17038 posts, RR: 66
Reply 1, posted (7 years 1 month 2 weeks 4 days 20 hours ago) and read 8567 times:

Assuming you were in level flight and trimmed, the nose would go down. The stabilizer is pushing down on the tail to hold the nose up in level flight. Take away the downforce from the stabilizer and the aircraft would pivot around the wing. What the final attitude would be is anybody's guess.

Quoting Flexo (Thread starter):
Also: Would there be any chance of keeping the aircraft under control after the loss of such an essential part?

No.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 2, posted (7 years 1 month 2 weeks 4 days 20 hours ago) and read 8541 times:

Quoting Flexo (Thread starter):
Ok, I found myself wondering what would happen if you were to lose the horizontal stabilizer in mid flight (i.e. seperated from the fuselage).
Obviously you would be in bad trouble, but would the nose go up or down?

Starlionblue has it right...the nose will go down. The horizontal stabilizer on all modern transports pushes down to maintain constant pitch attitude. The CG is ahead of the wing center of pressure, which tends to make the nose go down, and the wing itself has a moment that tends to drive it towards a lower angle-of-attack. The horizontal stabilizer has to balance out both these forces.

If you lose the stabilizer there's nothing to counteract these moments and the aircraft will lose control very quickly. This happened to a 707 in Luanda a couple of decades ago. It became a standard case study in the perils of fail-safe design.

Tom.


User currently offlineZANL188 From United States of America, joined Oct 2006, 3521 posts, RR: 0
Reply 3, posted (7 years 1 month 2 weeks 4 days 20 hours ago) and read 8537 times:
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Quoting Starlionblue (Reply 1):
Also: Would there be any chance of keeping the aircraft under control after the loss of such an essential part?

No.

 checkmark 

See the remarks at this website re: Aug 86 Aeromexico accident. This flight did not do well without its horizontal stab.

http://web.mit.edu/6.933/www/Fall2000/mode-s/collisions.html



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User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 4, posted (7 years 1 month 2 weeks 4 days 19 hours ago) and read 8528 times:

Quoting Flexo (Thread starter):
Would there be any chance of keeping the aircraft under control after the loss of such an essential part?

I cannot think of a single example of a successful outcome.

I have heard of surviving loss of vertical fin and rudder. I've survived loss of control of my rudder and a good friend lost control of ailerons and elevator but the sufaces and the weight & wetted area represented by those surfaces remained with us.

This is pretty much what it looks like.

I remember this one very well. I was in Vietnam when this happened and I don't think there was one aircrew member there who didn't see (and shudder at) this picture.

Sadly it was not only "friendly fire" but was a ceremonial round that didn't even "need" to be fired.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 5, posted (7 years 1 month 2 weeks 4 days 19 hours ago) and read 8525 times:

Quoting Starlionblue (Reply 1):
The stabilizer is pushing down on the tail to hold the nose up in level flight.



Quoting Tdscanuck (Reply 2):
Starlionblue has it right...the nose will go down.

Not always the case.... Some horizontal stabilizers provide an upward lift....thus causing the nose to trim down. In that case, if you lost the stab the nose would pitch up. The Saab 340 is a good example.... it has an inverted airfoil for its horizontal stabilizer

[Edited 2007-07-30 23:16:33]


"It's not the size of the dog in the fight, but the size of the fight in the dog"
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17038 posts, RR: 66
Reply 6, posted (7 years 1 month 2 weeks 4 days 19 hours ago) and read 8503 times:

Quoting SlamClick (Reply 4):
I have heard of surviving loss of vertical fin and rudder. I've survived loss of control of my rudder and a good friend lost control of ailerons and elevator but the sufaces and the weight & wetted area represented by those surfaces remained with us.

This is actually an interesting point. The fin is important but not essential for survival like the stabilizer. The aircraft is (relatively) stable in the yaw axis since it is symmetrical and it is possible to retain control without the the fin and rudder.

As long as you do retain wing and stabilizer and no fin you can still control the aircraft with differential thrust, roll and so forth. Your results may vary.

Quoting EMBQA (Reply 5):
ot always the case.... Some horizontal stabilizers provide an upward lift....thus causing the nose to trim down. In that case, if you lost the stab the nose would pitch up. The Saab 340 is a good example.... it has an inverted airfoil for its horizontal stabilizer

Indeed. And there are relaxed stability designs. But in all cases the result will be the same.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 7, posted (7 years 1 month 2 weeks 4 days 19 hours ago) and read 8490 times:
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Quoting Starlionblue (Reply 1):
Assuming you were in level flight and trimmed, the nose would go down.

This is precisely what happened to the lead P-51 in the recent Oshkosh accident. The left side horizontal stab was chewed up by a propeller, causing the airplane to nose into the ground. Fortunately for that pilot, he was already flaring for landing, and skidded to a stop with his tail in the air.


2H4




Intentionally Left Blank
User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 8, posted (7 years 1 month 2 weeks 4 days 19 hours ago) and read 8476 times:

Quoting Starlionblue (Reply 6):
But in all cases the result will be the same.

Correct.. but you can't hold what you said above to be 100% true every time. In some cases the nose will pitch up... not down as you said......but never the less, control be lost.



"It's not the size of the dog in the fight, but the size of the fight in the dog"
User currently offlineSEPilot From United States of America, joined Dec 2006, 6906 posts, RR: 46
Reply 9, posted (7 years 1 month 2 weeks 4 days 18 hours ago) and read 8471 times:

The IFR loss of control accident happens when the pilot loses situational awareness, usually entering the "graveyard spiral". This is a descending spiral with a bank angle exceeding 60 deg, and the first thing the pilot usually realizes is that he is descending rapidly, so he pulls on the yoke. This only tightens the spiral, does not halt the descent, and causes the pilot to pull harder. The result is that the tail fails from overload, the plane loses all control and the wings usually come off as well. It is invariably fatal. As to the initial question, the aft CG limit is always, I believe, still forward of the center of lift, so without the tail the nose will pitch down.

Quoting EMBQA (Reply 5):
Some horizontal stabilizers provide an upward lift....thus causing the nose to trim down. In that case, if you lost the stab the nose would pitch up. The Saab 340 is a good example.... it has an inverted airfoil for its horizontal stabilizer

I would dispute this. The fact that the airfoil is inverted indicates that it is producing down force, not upward force.
It of course would be possible to design a plane with a lifting tail; in fact this is what canard designs do. The disadvantage of canard designs is that the CG range is much narrower than with a conventional tail; I do not understand why. Anyone have any insight?



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offline777236ER From , joined Dec 1969, posts, RR:
Reply 10, posted (7 years 1 month 2 weeks 4 days 18 hours ago) and read 8464 times:

Quoting EMBQA (Reply 5):
Some horizontal stabilizers provide an upward lift....thus causing the nose to trim down. In that case, if you lost the stab the nose would pitch up. The Saab 340 is a good example.... it has an inverted airfoil for its horizontal stabilizer

I doubt the Saab 340's horizontal stabiliser provides a component of force upwards. To be dynamically stable, the centre of pressure must be behind the centre of mass, therefore to be statically stable, the horizontal stabilier should create a force vector downwards. Saab 340s aren't falling out of the sky every day, so the horizontal stabiliser is doing what all others do on commercial aircraft.

In fact, I seem to remember that the Saab 340 started off with a symmetric airfoil for the horizontal stabiliser. This caused dynamic stability problems with flap use, resulting in the inverted airfoil seen today.


User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 11, posted (7 years 1 month 2 weeks 4 days 18 hours ago) and read 8457 times:
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Quoting 777236ER (Reply 10):
I doubt the Saab 340's horizontal stabiliser provides a component of force upwards.

If I'm not mistaken, I believe the only horizontal stabilizers that provide upward force are those found on canards...


2H4




Intentionally Left Blank
User currently offlineJhooper From United States of America, joined Dec 2001, 6204 posts, RR: 12
Reply 12, posted (7 years 1 month 2 weeks 4 days 18 hours ago) and read 8456 times:

Quoting Flexo (Thread starter):
but then again the horizontal stabilizer probably produces some lift so

The horizontal stabilizer does produce lift, but in the opposite direction than the wings do. This helps in the longitudinal stability of the airplane. With the center of gravity being ahead of the lift, as the airplane speeds up in a dive, the downforce on the tail increases and this tends to bring the nose up. As the airspeed decreases in the resulting climb, the downforce on the tail decreases and allows the nose to fall. This creates oscillations about the lateral axis and allows one to trim the airplane to favor a certain airspeed. Without this stabilizing force, the airplane is uncontrollable.



Last year 1,944 New Yorkers saw something and said something.
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 13, posted (7 years 1 month 2 weeks 4 days 18 hours ago) and read 8440 times:

Quoting 2H4 (Reply 11):
If I'm not mistaken, I believe the only horizontal stabilizers that provide upward force are those found on canards...

As stated, not exactly correct. They would provide upward force any time the CG of the plane falls between the center of pressure of the wings and that of the horizontal stab. That is, in an aft CG condition in a conventional airplane and in a forward CG condition in a design with canards.

"forward" and "aft" are used in a relative sense here, not an absolute one.

Quoting Jhooper (Reply 12):
The horizontal stabilizer does produce lift, but in the opposite direction than the wings do.

Again, see the above.

Many planes could be loaded to a point where the tail is more or less neutrally loaded, or to some range either side of that. Most jet transports are designed to be loaded favoring aft CG stations and normal takeoff stab trim settings are in units of nose UP. But it could be otherwise.

In general aft CG gives less drag at cruise and therefore better economy. Forward CG gives better control.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 14, posted (7 years 1 month 2 weeks 4 days 7 hours ago) and read 8311 times:

Quoting SEPilot (Reply 9):
The disadvantage of canard designs is that the CG range is much narrower than with a conventional tail; I do not understand why. Anyone have any insight?

A canard design tends to put most of the fuel behind the CG, which causes a bigger CG swing than a conventional arrangement as you burn fuel. Since the total CG range is fixed by the control authority of the canard, the allowable CG range for everything else is much tighter.

Quoting SlamClick (Reply 13):
They would provide upward force any time the CG of the plane falls between the center of pressure of the wings and that of the horizontal stab.

If this happened, the airplane would flip on its back the first time it hit a gust. Operating in such a condition would be dynamically unstable and extremely dangerous.

Tom.


User currently offlineSEPilot From United States of America, joined Dec 2006, 6906 posts, RR: 46
Reply 15, posted (7 years 1 month 2 weeks 4 days 5 hours ago) and read 8276 times:

Quoting Tdscanuck (Reply 14):
A canard design tends to put most of the fuel behind the CG, which causes a bigger CG swing than a conventional arrangement as you burn fuel. Since the total CG range is fixed by the control authority of the canard, the allowable CG range for everything else is much tighter.

Thanks for the info, I did not realize this. I always wondered why the CG range for a canard was tighter.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineOly720man From United Kingdom, joined May 2004, 6723 posts, RR: 11
Reply 16, posted (7 years 1 month 2 weeks 4 days 4 hours ago) and read 8259 times:

Quoting SlamClick (Reply 4):
I have heard of surviving loss of vertical fin and rudder.

http://www.talkingproud.us/HistoryB52NoTail.html

On January 10, 1964, Boeing civilian test pilot Chuck Fisher and his three man crew lost their tail, the tail of their B-52H Stratofortress that is, at about 14,000 ft. over northern New Mexico's Sangre de Christo mountains. Their mission was to shake, rattle and roll this big beast at high speed and low altitude to record sensor data on how such a profile affected the B-52's structure. They did their job. The vertical stabilizer blew off. Six hours later and after a lot of engineering on the ground and in the air, Fisher brought his B-52 home, with the coveted data.



wheat and dairy can screw up your brain
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 17, posted (7 years 1 month 2 weeks 4 days 2 hours ago) and read 8217 times:

Quoting Tdscanuck (Reply 14):
If this happened, the airplane would flip on its back the first time it hit a gust.

What ever are you talking about?

It can't work any other way.

The CG is the effective weight of the entire airplane. In unaccelerated flight this is always a DOWN force.
The center of lift in non-inverted flight is an UP force.
The horizontal stabilizer - elevator - trim assembly is the effort one puts against the lever to keep the whole thing level.

Now how could you balance a weight between the fulcrum and the force you are applying without exerting effort against gravity at that point? In other words UP.

If the weight was on the other side of the fulcrum from your force then it would take DOWNward effort to hold the weight up. Teetertotters would be really interesting to watch, were it otherwise.

By the way, planes don't simply flip over for a number of reasons, not the least of which is that the tailplanes act rather like the feathers on an arrow. The farther you try to displace them from "trail" the greater the airload pressing them back.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 18, posted (7 years 1 month 2 weeks 3 days 22 hours ago) and read 8120 times:

Quoting SlamClick (Reply 17):
Quoting Tdscanuck (Reply 14):
If this happened, the airplane would flip on its back the first time it hit a gust.

What ever are you talking about?

Dynamic stability.

If the CG is behind the center of pressure of the wing you can be statically stable by having just the right amount of upward force on the horizontal stabilizer. However, if you run into a gust you will be unstable. As the gust hits the wing the angle of attack (and hence lift) will increase. This pitches the nose up, causing a further increase in angle of attack, causing a further increase in left, etc.

Dynamic stability requires that the CG be ahead of the center of pressure so that the disturbance results in a corrective moment, not one that increases the disturbance.

Quoting SlamClick (Reply 17):
The CG is the effective weight of the entire airplane. In unaccelerated flight this is always a DOWN force.
The center of lift in non-inverted flight is an UP force.
The horizontal stabilizer - elevator - trim assembly is the effort one puts against the lever to keep the whole thing level. Now how could you balance a weight between the fulcrum and the force you are applying without exerting effort against gravity at that point? In other words UP.

No argument from me there. The configuration you're describing is statically stable only though. It's dynamically unstable. That's why you only see such an arrangement in aircraft with augmented stability (i.e. fighters).

Tom.


User currently offlineAeroWeanie From United States of America, joined Dec 2004, 1609 posts, RR: 52
Reply 19, posted (7 years 1 month 2 weeks 3 days 21 hours ago) and read 8095 times:
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In some trimmed flight conditions, the horizontal tail of a conventionally configured aircraft can be uploaded, due to the pitching moments created by the other components of the aircraft. However, it is usually downloaded.

Somewhere, I have a series of pictures of a B-17 where the horizontal tail gets hit and removed by the bomb of a B-17 above it. In the sequence, it noses over, like theory says it would.

Also, if the tail of a aircraft stalls, the same thing happens. On the first flight of the IsrAviation ST-50, when the flaps were put down, the tail stalled and the aircraft pitched down and went into an inverted spin. Luckily, the pilot (Norm Howell) thought quick and recovered by retracting the flaps.


User currently offlineMDorBust From , joined Dec 1969, posts, RR:
Reply 20, posted (7 years 1 month 2 weeks 3 days 20 hours ago) and read 8054 times:

Quoting Tdscanuck (Reply 18):
If the CG is behind the center of pressure of the wing you can be statically stable by having just the right amount of upward force on the horizontal stabilizer. However, if you run into a gust you will be unstable. As the gust hits the wing the angle of attack (and hence lift) will increase. This pitches the nose up, causing a further increase in angle of attack, causing a further increase in left, etc.

And this is why we invented moveable flight controls.

So you can adjust the amount of force acting upon the lever and compensate for the new force and bring the system back into equalibrium.

I do hope you realize there are a great many aircraft flying with CGs aft of the Center of Lift.


User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 21, posted (7 years 1 month 2 weeks 3 days 7 hours ago) and read 7934 times:

Quoting Tdscanuck (Reply 18):
Dynamic stability requires that the CG be ahead of the center of pressure so that the disturbance results in a corrective moment, not one that increases the disturbance.

You're mixing up static and dynamic stability though. Static stability is when the aircraft will want to return to the trimmed AoA following an upset. Dynamic instability is when the aircraft will fly a phugoid of increasing amplitude at this AoA if left to its own devices.



I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 22, posted (7 years 1 month 2 weeks 3 days 6 hours ago) and read 7913 times:

Quoting FredT (Reply 21):
You're mixing up static and dynamic stability though. Static stability is when the aircraft will want to return to the trimmed AoA following an upset. Dynamic instability is when the aircraft will fly a phugoid of increasing amplitude at this AoA if left to its own devices.

You're right, my bad. Thank you for the clarification.

Quoting FredT (Reply 21):
I do hope you realize there are a great many aircraft flying with CGs aft of the Center of Lift.

Yes.

How many of them have augmented stability? For those that don't, how are they stable?

Tom.


User currently offlineKieron747 From , joined Dec 1969, posts, RR:
Reply 23, posted (7 years 1 month 2 weeks 3 days 3 hours ago) and read 7866 times:

Quoting SlamClick (Reply 4):
I have heard of surviving loss of vertical fin and rudder.

How odd I was going to ask you guys about this only the other day... I was wondering if a modern plane could survive such a loss, and was therefore going to ask about the details of the importance of the fin.

When the AA airbus crashed after loss of the fin in New York,.. was that survivable, i.e was the plane controllable after the loss? Or did more that just the fin come away, the horizontal stabilizer too?

Regards,

Kieron747


User currently offlineSEPilot From United States of America, joined Dec 2006, 6906 posts, RR: 46
Reply 24, posted (7 years 1 month 2 weeks 3 days 3 hours ago) and read 7860 times:

Quoting Kieron747 (Reply 23):

When the AA airbus crashed after loss of the fin in New York,.. was that survivable, i.e was the plane controllable after the loss? Or did more that just the fin come away, the horizontal stabilizer too?

That's an interesting question; I have wondered about it as well. As far as I know, the initial event was the loss of the vertical stabilizer only. The fact that the plane was at relatively low altitude (the B-52 was IIRC at fairly high altitude) gave the crew far fewer alternatives as far as actions they could take; it also is important exactly what attitude the plane was at when the stabilizer departed. Due to the fact that the Airbus subsequently shed both engines after the fin and before it crashed leads me to believe that the fin departed when the plane was in a yawed position and proceeded to become totally unstable, whereas the B-52 was able to recover stability and therefore must have been in a relatively coordinated attitude when it lost its fin.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
25 Starlionblue : The best modern example I can think of is the JAL 747 accident in which more than half the fin was blown off after a pressure bulkhead ruptured (inco
26 SEPilot : I was thinking about that one as well, and am still puzzled as to why the B-52 was able to land successfully and this one was not. As you say, they d
27 SlamClick : This event also severed lines on all the hydraulic systems. Whole different problem. The plane was almost 100% uncontrollable. Including Kyu Sakamoto
28 Tdscanuck : Loss of hydraulics was a big factor in the JAL accident. The JAL flight didn't lose total control but they had an enormous phugoid-type oscillation.
29 777236ER : None of them are certified commercial aircraft. No, that's why we invented FBW. Control surfaces only control dynamically unstable aircraft when the
30 Starlionblue : As mentioned. There is a great docu about this. They show the flight path and it looks like the squiggles my daughter draws. Indeed, "relaxed stabili
31 Post contains images 777236ER : I think the chain of accidents caused by the loss of all hydraulics on large airliners is impressive. First we have JAL 123, a true disaster. From th
32 SlamClick : Unfortunately we also have the Turkish Airlines DC-10 near Paris and American 191 at Chicago which had way too much in common. Each initiating event
33 777236ER : Hopefully, we've seen the end of aircraft-wide hydraulic systems for new-build large aircraft with the advent of power by wire. The A380 has EHAs (El
34 Starlionblue : Don't they also have a bus instead of individual wiring links? That way the system will just reroute commands if a wire is severed.
35 MDorBust : That's because there is no point to design an aft CG into a commercial aircaft. Which doesn't change the point that the are a great many aft CG aircr
36 777236ER : The EHAs and EBHAs run off three AC electrical buses on the A380. In the empennage of the A380 you end up with control surfaces powered by the green
37 Starlionblue : AFAIK no. If the CG was aft of the center of lift they would be dynamically unstable and need FBW for control.
38 777236ER : Not that many. There's no need for the attitude. Control surfaces don't make dynamically unstable aircraft stable, FBW does. Nope. Might have been cl
39 Starlionblue : F-16 is only barely unstable. The list of dynamically unstable aircraft is actually quite short and does not include most modern front line fighters.
40 SEPilot : I can still conceive of a structural failure destroying all the buses leading to the tail but leaving the tail intact; the difference would be presum
41 FredT : That wasn't me you quoted BTW. Cheers, /Fred
42 Post contains links Tdscanuck : I believe they're used for some of the spoilers. I don't think they're used as extensively as they are on the A380 though. It's both. You can't run e
43 Kay : What about that accident in NY in 2001 or 2002? It was an Airbus A300 (or A310)? there was turbulence from the preceding aircraft, and this one lost
44 Starlionblue : Low speed, low altitude, heavy turbulence. By all accounts after the fin broke other parts broke off too. Had this been at cruise with only the fin l
45 Tdscanuck : The fin separated because the FO made some enormous rudder inputs that took the fin attachment beyond it's static limit. So, when the fin left, there
46 Kay : Interesting. Is the scenario of an airliner coming in and landing without a vertical fin perceivable? Kay
47 3MilesToWRO : I'll put it this way: do birds have vertical fin?
48 Tdscanuck : I think it's perceivable. I'm not a pilot so I don't know how practical it is. The issue I can see is that you would have very limited yaw stability
49 SlamClick : Yes. In a manner of speaking. Their tails can be rotated about their longitudinal axis, giving yaw control. An airplane's horizontal stab cannot do t
50 SEPilot : The vertical stabilizer is the only control element that a plane has successfully landed without; see the B-52 incident detailed above. No plane has
51 SlamClick : Airliners - don't know and would not like to bet on it. Light plane, it has happened. A friend of mine was instructing in a common trainer of forty y
52 Post contains links 2H4 : Oh, I beg to differ... I've approached an airport and landed safely without ever moving the ailerons. It was a fun lesson. 2H4
53 Kay : Magnificient story. And unfortunately goes where some of my worst fears are. what if a control cable snaps or malfunctions... Only last week I was fl
54 AeroWeanie : Not quite. What the FO did was step on the pedals at just the right frequency to excite the Dutch Roll mode of the aircraft (a dynamic stability mode
55 SEPilot : Amazing. I wouldn't have believed it possible. I don't believe it would have with anything other than a jet fighter. There's a big difference between
56 Post contains images 2H4 : Ahhh....now the fine print comes out! 2H4
57 411A : One need look no further than what happened to a B707 on approach in Africa years ago when, as the landing flaps (50 degrees) were being selected, the
58 2H4 : The landing flare. 2H4
59 411A : The landing flare is incorrect.
60 Blackbird : 411A, Takeoff? Andrea Kent Pi is approximately equal to 3.1415926535 and so on
61 411A : Takeoff is correct, specifically the rotation maneuver, especially in long body heavy weight aircraft, with full (or nearly full) center tank fuel. Th
62 XT6Wagon : There has been some cases. The F15 that was involved in a mid-air lost the horizontal stablilizer ont hat side, control remained as it removed nearly
63 BAe146QT : I was just thinking the same thing, but you beat me to it. I wonder if Boeing, in their experiments with tailless, low-observability drones ever trie
64 Post contains images 3MilesToWRO : You are absolutely sure that never, in absolutely no case, has the plane survived loss of half of stabilizer? It's a very brave statement, I must say
65 Tdscanuck : I suspect someone thought of it, but split ailerons is a far simpler way to achieve similar control. Tom.
66 2H4 : Interesting, thanks for the info. Would this still be the case if the center fuel tank was empty, or is the increased stress on the horizontal stabil
67 DeltaGuy : Having witnessed the crash with my own eyes last week, that too was very hairy. Not something I hope to ever see again in this lifetime. The survivor
68 411A : According to a Boeing flight test engineer I spoke with recently, yes, about the same, just slightly more with the CofG far forward, as it would be w
69 SEPilot : Sorry about that, I should have added "that I know of." My bad.
70 MD-90 : I believe that the Piaggio P.180's horizontal tail provides lift as well. Since it doesn't have a true canard, all three flying surfaces provide lift
71 Post contains images 2H4 : Ha, that's a great bit of trivia. 2H4
72 Post contains links and images JetMech : A classic case in point. China Airlines Flight 006 (February 19, 1985) from Taipei to Los Angeles ( B747SP ) had an engine failure in flight at cruis
73 SEPilot : I was aware of this incident; it did not lose half the horizontal stabilizer. It did lose pretty nearly half the elevator, though.
74 Starlionblue : As I recall, that 747SP was repaired and put back into service. But just as a car after a bad crash, it was permanently bent in some places. This may
75 SlamClick : The linked NTSB report does indeed confirm that. It states that the wings were bent upward about two inches but that was well within the standards se
76 Post contains images Nohag : Probably one of the most stupid remarks/toughts but here I go: A horizontal stabilizer is just a "horizontal" stabilizer because it's orientation is m
77 Starlionblue : "Finish him!" "COMBO!" "FATALITY" :D
78 SlamClick : Thus enabling the pilot to impact the ground with the underside of the aircraft instead of the windshield. That might be an improvement.
79 Post contains images Nohag : OK guys it was just a tought! In PPL class you learn the ever changing impact and effectiveness of the control surfaces during the different stages o
80 Starlionblue : No and yes. That is, redundancy is provided by two stabilizer "arms", each (presumably) with two spars. I guess the reasoning is that if the entire s
81 Mrocktor : Actually, there is. Using down force for balance means you are creating useless induced drag. You create induced drag due to the down force and you c
82 Post contains links IADCA : Take a look at the photo taken from the rear of the aircraft shown with about 25 seconds left in the video about it http://www.youtube.com/watch?v=-_
83 CoolGuy : I still don't have a feel for what any of the surfaces at the rear of the plane actually do, except for the elevator. Anywhere I could go to understan
84 Tdscanuck : Go to a playground and get on the teeter totter. If you sit directly over the hinge you're balanced but if you're away from the hinge the teeter tott
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