Missing Malaysia Airlines jet carrying 239 triggers Southeast Asia search

[skippybangkok]

If an aircraft loses power, it's not likely to be both engines at the same time. We have been told that the autopilot can correct for the problems that causes.

But if the second engine also starves out, the autopilot disconnects. Right?

Now fixed wing aircraft are nose-heavy. They carry a little more weight in front of the point of lift of the wings. Ever had a balsa wood toy glider that you had to stick a lead weight in the nose so it would fly?

So even if by some miracle during total fuel starvation the plane could get straight and level, it would automatically go nose low to maintain airspeed and stability. There would be no one and nothing to cause it to flare just before touching the water and it would nose right in. There is also no reason to think that it would be straight and wings level.

There is, if it was gliding nicely unpiloted, only the assurance that it would go nose low and hit the water with that attitude.

Maybe said have paid more attention aerodynamics class Or experiment more w paper aeroplanes

Sent from my iPhone using Thaivisa Connect Thailand mobile app

[hawker9000]

At engines-out and loss of autopilot (assuming some mode was engaged in the 1st place), would the elevators remain in the last-commanded position or fare into the relative wind or what? If they merely maintain last position, and that position was slightly nose-up (to compensate for the aircraft being slightly nose-heavy), then what would happen after the aircraft went into its power-off dive? As airspeed increased, and airflow over the tail increased, would the elevators start to produce more & more lift ('guess that would actually be negative or "downward" lift) and nose-up force? If so, could it cause the aircraft to conceivably even enter a stall condition?

[skippybangkok]

Commercial jets are aerodynamically stable in all axis

If all went off, it would basically descend at the last IAS which would usually have some nose down

Contrary to popular belief:-

Power is for up and down

Elevators are for speed

Sent from my iPhone using Thaivisa Connect Thailand mobile app

Edited May 3, 2014 by skippybangkok

[catterwell]

Commercial jets are aerodynamically stable in all axis

If all went off, it would basically descend at the last IAS which would usually have some nose down

Contrary to popular belief:-

Power is for up and down

Elevators are for speed

Sent from my iPhone using Thaivisa Connect Thailand mobile app

Quite different from the Chipmunk, which is delightfully unstable and great for aerobatics. If you take your hands off the stick, it goes all over the place. In my day, we used ailerons for turning, along with a bit of rudder to avoid side-slip. We also had flaps to change the aerofoil profile for slow speed. In England, we call elevators "lifts" and I've never flown a plane fitted with them.

Ah yes, I recall now. Elevators are those bits that go up and down at the back. I never had much use for them except when looping the loop. On the other hand, I've never flown any aircraft with any sane person as a willing passenger.

Edited May 3, 2014 by catterwell

[catterwell]

Commercial jets are aerodynamically stable in all axis

If all went off, it would basically descend at the last IAS which would usually have some nose down

Contrary to popular belief:-

Power is for up and down

Elevators are for speed

Sent from my iPhone using Thaivisa Connect Thailand mobile app

My Chipmunk elevators pushed my nose up or down. But I'm curious how they're used for speed. Do you flap them like a mermaid's tail? Please explain how "elevators are for speed".

[hawker9000]

Commercial jets are aerodynamically stable in all axis

If all went off, it would basically descend at the last IAS which would usually have some nose down

Contrary to popular belief:-

Power is for up and down

Elevators are for speed

Sent from my iPhone using Thaivisa Connect Thailand mobile app

My Chipmunk elevators pushed my nose up or down. But I'm curious how they're used for speed. Do you flap them like a mermaid's tail? Please explain how "elevators are for speed".

It's a ground school rubric. Say your flying a glideslope on an approach. If you go above GS, the thing to do is reduce power, not lower the nose. If you get fast on an approach, the thing to do is raise the nose rather than reduce power.

[khaosai]

Commercial jets are aerodynamically stable in all axis

If all went off, it would basically descend at the last IAS which would usually have some nose down

Contrary to popular belief:-

Power is for up and down

Elevators are for speed

Sent from my iPhone using Thaivisa Connect Thailand mobile app

My Chipmunk elevators pushed my nose up or down. But I'm curious how they're used for speed. Do you flap them like a mermaid's tail? Please explain how "elevators are for speed".

Hi,

I think it's fair and simplistic to say you can use both pitch and thrust to control speed during normal operations.

If for instance the aircrafts required indicated airspeed reduces close to the ground I certainly would not pitch forward to return the speed to where it should be, increasing thrust would be far more appropriate.

Different training organisations teach different methods with regards to pitch and power to maintain profile. Keep it simple, use nice smooth inputs to both to achieve the desired result.

[hawker9000]

...getting OT. Skippy made the statement that the aircraft would after losing both engines simply maintain its last established IAS, which implies whatever pitch angle and rate of descent it takes to maintain that IAS. And he stated immediately prior that all airliners are dynamically stable in all 3 axes. Does "stability" imply this ability to take up & then maintain a constant-speed descent with no power on the aircraft, and thus nothing driving (and further, no movement of) the elevators?

So let's say MH370 is cruising at .84M equals about what, 480KIAS? According to skippy, when the engines fail and autopilot goes away, MH 370 takes up a descent at 480KIAS and flies it all the way down. I'm not sure what vertical speed that represents, but I'm pretty sure the plane would be smacking the wavetops pretty hard...

Edited May 3, 2014 by hawker9000

[catterwell]

Commercial jets are aerodynamically stable in all axis

If all went off, it would basically descend at the last IAS which would usually have some nose down

Contrary to popular belief:-

Power is for up and down

Elevators are for speed

Sent from my iPhone using Thaivisa Connect Thailand mobile app

My Chipmunk elevators pushed my nose up or down. But I'm curious how they're used for speed. Do you flap them like a mermaid's tail? Please explain how "elevators are for speed".

It's a ground school rubric. Say your flying a glideslope on an approach. If you go above GS, the thing to do is reduce power, not lower the nose. If you get fast on an approach, the thing to do is raise the nose rather than reduce power.

Thank you, I think I've got it. Can you lend me a plane to have a go? (My PPL expired decades ago, but my bpen rai).

[hawker9000]

Commercial jets are aerodynamically stable in all axis

If all went off, it would basically descend at the last IAS which would usually have some nose down

Contrary to popular belief:-

Power is for up and down

Elevators are for speed

Sent from my iPhone using Thaivisa Connect Thailand mobile app

My Chipmunk elevators pushed my nose up or down. But I'm curious how they're used for speed. Do you flap them like a mermaid's tail? Please explain how "elevators are for speed".

It's a ground school rubric. Say your flying a glideslope on an approach. If you go above GS, the thing to do is reduce power, not lower the nose. If you get fast on an approach, the thing to do is raise the nose rather than reduce power.

Thank you, I think I've got it. Can you lend me a plane to have a go? (My PPL expired decades ago, but my bpen rai).

Well, I can tell you that at the boat, naval aviators follow that guidance pretty religiously, maintaining a constant AOA ("onspeed") right up until touchdown. If going above (GS), one reduces power and if below one adds power. If one gets "slow", indicated by increasing angle-of-attack, one lowers the nose. So, the rule has plenty of validity, just maybe not in the case of a 777 with no engines in a descent...

Edited May 3, 2014 by hawker9000

[khaosai]

...getting OT. Skippy made the statement that the aircraft would after losing both engines simply maintain its last established IAS, which implies whatever pitch angle and rate of descent it takes to maintain that IAS. And he stated immediately prior that all airliners are dynamically stable in all 3 axes. Does "stability" imply this ability to take up & then maintain a constant-speed descent with no power on the aircraft, and thus nothing driving (and further, no movement of) the elevators?

Hi,

so many variables, and as stated earlier it's unlikely both engines stopped at exactly the same time. All this also assumes the aircraft did not achieve a controlled ditching under power.

I would imagine with both engines failed, no autopilot, and no one flying the aircraft then the following may occur:

Pitch down, height loss, acceleration, pitch up, speed loss, pitch down and so on until stall resulting in a large impact with the ocean.

A much less likely scenario similar to the above, but resulting in a much smoother belly contact, wings level. Highly unlikely.

[khaosai]

...getting OT. Skippy made the statement that the aircraft would after losing both engines simply maintain its last established IAS, which implies whatever pitch angle and rate of descent it takes to maintain that IAS. And he stated immediately prior that all airliners are dynamically stable in all 3 axes. Does "stability" imply this ability to take up & then maintain a constant-speed descent with no power on the aircraft, and thus nothing driving (and further, no movement of) the elevators?

So let's say MH370 is cruising at .84M equals about what, 480KIAS? According to skippy, when the engines fail and autopilot goes away, MH 370 takes up a descent at 480KIAS and flies it all the way down. I'm not sure what vertical speed that represents, but I'm pretty sure the plane would be smacking the wavetops pretty hard...

Hi,

The indicated speed would be much less than 480 knots. More like 270 knots indicated. 480 knots would be close to the true airspeed however.

[hawker9000]

...getting Oaircrapy made the statement that the aircraft would after losing both engines simply maintain its last established IAS, which implies whatever pitch angle and rate of descent it takes to maintain that IAS. And he stated immediately prior that all airliners are dynamically stable in all 3 axes. Does "stability" imply this ability to take up & then maintain a constant-speed descent with no power on the aircraft, and thus nothing driving (and further, no movement of) the elevators?

Hi,

so many variables, and as stated earlier it's unlikely both engines stopped at exactly the same time. All this also assumes the aircraft did not achieve a controlled ditching under power.

I would imagine with both engines failed, no autopilot, and no one flying the aircraft then the following may occur:

Pitch down, height loss, acceleration, pitch up, speed loss, pitch down and so on until stall resulting in a large impact with the ocean.

A much less likely scenario similar to the above, but resulting in a much smoother belly contact, wings level. Highly unlikely.

Skippy is saying otherwise. Ya' can't both be right!

Also, the engines may fail one at a time, but the autopilot surely doesn't give up with one good engine, and surely is designed to handle one engine-out (i.e., all the asymmetric thrust implications).

BTW, does a 777 have something like a ram air turbine that can provide essential electrical power even with all generators or both engines off? If so, is there an aux. hydraulic pump powered by it?

Edited May 3, 2014 by hawker9000

[canuckamuck]

Not a pilot, but I would assume the autopilot isn't to going make a nice flare for a water landing when there clearly is no runway.

Any way you look at it, no fuel is certainly going to equal a bust up plane on impact with the ocean.

[hawker9000]

Not a pilot, but I would assume the autopilot isn't to going make a nice flare for a water landing when there clearly is no runway.

Any way you look at it, no fuel is certainly going to equal a bust up plane on impact with the ocean.

Agreed, but one theory holds that the pilot flew up to the point of fuel exhaustion and then ditched in order to increase the odds of the airplane coming down as intact as possible, so as to sink as intact as possible, so as to minimize floating debris and frustrate any search efforts as much as possible.

[khaosai]

...getting OT. Skippy made the statement that the aircraft would after losing both engines simply maintain its last established IAS, which implies whatever pitch angle and rate of descent it takes to maintain that IAS. And he stated immediately prior that all airliners are dynamically stable in all 3 axes. Does "stability" imply this ability to take up & then maintain a constant-speed descent with no power on the aircraft, and thus nothing driving (and further, no movement of) the elevators?

Hi,

so many variables, and as stated earlier it's unlikely both engines stopped at exactly the same time. All this also assumes the aircraft did not achieve a controlled ditching under power.

I would imagine with both engines failed, no autopilot, and no one flying the aircraft then the following may occur:

Pitch down, height loss, acceleration, pitch up, speed loss, pitch down and so on until stall resulting in a large impact with the ocean.

A much less likely scenario similar to the above, but resulting in a much smoother belly contact, wings level. Highly unlikely.

Skippy is saying otherwise. Ya' can't both be right!

Also, the engines may fail one at a time, but the autopilot surely doesn't give up with one good engine, and surely is designed to handle one engine-out (i.e., all the asymmetric thrust implications).

Hi,

I am not saying I am right and skippy is wrong. I am giving my opinion and respect all ideas and opinions on the subject to what may have happened.

If in normal flight control mode the aircraft has the following functions available:

Stall protection, overspeed protection and bank angle protection. If the aircraft automatically goes to secondary mode, or pilot selected direct mode then these will not be available.

The autopilot is only available in the normal flight control mode.

The thrust asymmetry compensation is also only available in the normal flight control mode.

If both engines fail then the normal flight control mode is initially not available. It however can be reconnected by the pilot thus allowing the auto pilot to be re engaged once the auxiliary power unit starts. That however needs fuel too, so the implications of it not being available are obvious.

With both engines failed the ram air turbine (RAT) will automatically deploy. It provides both electrical and hydraulic power. Primary flight control components from the centre hydraulic system will continue to work via the RAT.

Edited May 3, 2014 by khaosai

[skippybangkok]

Having had to do Aerodynamic Stability calculations for final year exam, it left me with years of nightmares complete with LaPlace transformations

To explain simple for stability in pitch , from the nose going backwards the following applies:-

1. Center of a Gravity (CG ) is always in front of main wing center of lift

2. Main wing of course lifts

3. Horizontal stabiliser ( tail ) is a negative wing, meaning it pulls down like a formula one car tail wing.

Only reason you waste fuel on a wing that pulls you down to earth is - stability.

So Aerodynamic stability is easy to now fathom

1. In stable air/ constant speed, is you get gust of wind ( air speed increase ), more lift on main wing and more down pull on tail.

Nose will pitch up

2. If nose pitch up, angle of attack on tail will reduce resulting in less negative lift. Since CG is forward of main wing, this will pull nose down.

So what happens - add more engine power is same as a gust of wind, nose will pitch up. Since there are no "shock absorbers", it will be like a spring which oscillates for a while ( speed / pitch / vs ) will oscillate until new steady state

Simply put

Power controls vertical speed - up/down- alt hold

Sent from my iPhone using Thaivisa Connect Thailand mobile app

Edited May 3, 2014 by skippybangkok

[hawker9000]

Having had to do Aerodynamic Stability calculations for final year exam, it left me with years of nightmares complete with LaPlace transformations

To explain simple for stability in pitch , from the nose going backwards the(CG? llowing applies:-

1. Center of a Gravity (CG ) is always in front of main wing center of lift

2. Main wing of course lifts

3. Horizontal stabiliser ( tail ) is a negative wing, meaning it pulls down like a formula one car tail wing.

Only reason you waste fuel on a wing that pulls you down to earth is - stability.

So Aerodynamic stability is easy to now fathom

1. In stable air/ constant speed, is you get gust of wind ( air speed increase ), more lift on main wing and more down pull on tail.

Nose will pitch up

2. If nose pitch up, angle of attack on tail will reduce resulting in less negative lift. Since CG is forward of main wing, this will pull nose down.

So what happens - add more engine power is same as a gust of wind, nose will pitch up. Since there are no "shock absorbers", it will be like a spring which oscillates for a while ( speed / pitch / vs ) will oscillate until new steady state

Simply put

Power controls vertical speed - up/down- alt hold

Sent from my iPhone using Thaivisa Connect Thailand mobile app

Sorry, Skippy, just not what we're talking about. It's not a question of what happens in a gust of wind. It's what happens with both engines out, all the way down to the water that we're concerned with.

So there is a RAT which can provide hydraulic power to the flight controls, even with both engines out. The pilot, if still alive, COULD have attempted a controlled ditching.

If the pilot was not alive, then the question is what would the aircraft do on its own. Would the RAT deploy automatically? If so, would autopilot be restored and provide a "controlled" descent ( e.g., a reasonably stabilized ("stabilized" in terms of predictability and adherence to some programmed set of rules, not "stabilized" as in dynamically stable)? If so, even without a pilot at the controls maybe there could've been something other than a high-speed/high angle/high rate-of-descent impact.

Edited May 3, 2014 by hawker9000

[canuckamuck]

Not a pilot, but I would assume the autopilot isn't to going make a nice flare for a water landing when there clearly is no runway.

Any way you look at it, no fuel is certainly going to equal a bust up plane on impact with the ocean.

Agreed, but one theory holds that the pilot flew up to the point of fuel exhaustion and then ditched in order to increase the odds of the airplane coming down as intact as possible, so as to sink as intact as possible, so as to minimize floating debris and frustrate any search efforts as much as possible.

Which is plausible but just as unusual as all the other possibilities.

Whatever happened, it clearly wasn't a case of simple mechanical failure.

[P45Mustang]

Can I just confirm that I am not a pilot, but remain interested in the disappearance of MH370 KL-PEK.

I normally fly economy btw.

[NeverSure]

Understood. Thanks.

My reading of previous posts suggests that it would take great skill to land it on water with minimal damage.

No fuel, switched off autopilot and no pilot may be the best way of achieving it perhaps.

If an aircraft loses power, it's not likely to be both engines at the same time. We have been told that the autopilot can correct for the problems that causes.

But if the second engine also starves out, the autopilot disconnects. Right?

Now fixed wing aircraft are nose-heavy. They carry a little more weight in front of the point of lift of the wings. Ever had a balsa wood toy glider that you had to stick a lead weight in the nose so it would fly?

So even if by some miracle during total fuel starvation the plane could get straight and level, it would automatically go nose low to maintain airspeed and stability. There would be no one and nothing to cause it to flare just before touching the water and it would nose right in. There is also no reason to think that it would be straight and wings level.

There is, if it was gliding nicely unpiloted, only the assurance that it would go nose low and hit the water with that attitude.

The trim/auto trim features compensates for this if active. The FBW even has the trim able to compensate automatically during flare out for landing.

If the auto trim shuts off with the autopilot, even if it stayed where it was the plane would still go nose down as it slowed.

If by some miracle the plane stayed level as it went nose low, there would still be no auto trim to cause it to flare.

Lacking a pilot, it's going into the ocean nose low, and maybe even on its side.

Edited May 3, 2014 by NeverSure

[P45Mustang]

I reckon it's in the South China Sea or VietNam.

[Tywais]

I reckon it's in the South China Sea or VietNam.

I'm certain it's either in the Northern hemisphere or the Southern hemisphere. That about sums up all the information from the media.

[boomerangutang]

<script type='text/javascript'>window.mod_pagespeed_start = Number(new Date());</script>

Not a pilot, but I would assume the autopilot isn't to going make a nice flare for a water landing when there clearly is no runway.
Any way you look at it, no fuel is certainly going to equal a bust up plane on impact with the ocean.

Agreed, but one theory holds that the pilot flew up to the point of fuel exhaustion and then ditched in order to increase the odds of the airplane coming down as intact as possible, so as to sink as intact as possible, so as to minimize floating debris and frustrate any search efforts as much as possible.

I concur with the scenario painted above: Pilot remained alive, probably the only one on board still alive. If his intention was to ditch with as little debris, and in as remote a region as possible, he was wildly successful.

[skippybangkok]

Sorry, Skippy, just not what we're talking about. It's not a question of what happens in a gust of wind. It's what happens with both engines out, all the way down to the water that we're concerned with.

So there is a RAT which can provide hydraulic power to the flight controls, even with both engines out. The pilot, if still alive, COULD have attempted a controlled ditching.

If the pilot was not alive, then the question is what would the aircraft do on its own. Would the RAT deploy automatically? If so, would autopilot be restored and provide a "controlled" descent ( e.g., a reasonably stabilized ("stabilized" in terms of predictability and adherence to some programmed set of rules, not "stabilized" as in dynamically stable)? If so, even without a pilot at the controls maybe there could've been something other than a high-speed/high angle/high rate-of-descent impact.

What are the scenarios - capt dude dead or not?

If alive - sure can bring it down level and stable - have been a few examples with other AC over the years

If dead and auto pilot - would assume imbalance in fuel , one engine putter out first , leaving auto pilot to handle one engine which is usually not a great situation

Assuming autopilot can handle it, there would be rudder and aileron input to compensate for engine out, and when last engine and power drops off - assume that imbalance would be enough to put it in a spin.

Sent from my iPhone using Thaivisa Connect Thailand mobile app

Edited May 3, 2014 by skippybangkok

[P45Mustang]

It would seem we are all grasping at straws.

And that includes the Aussie search team.

[skippybangkok]

Yep...

Sent from my iPad using ThaiVisa app

[JesseFrank]

Have they actually checked if it isn't parked at KL airport ? I assume that would be the best place to hide it.

[hawker9000]

It would seem we are all grasping at straws.

And that includes the Aussie search team.

With this episode, there hasn't been a whole heckuva lot to grasp at otherwise.. So might as well let the imagination have free reign. One theory's almost as good as another. As the discussion has progressed, clearly, one guy's flight of fancy has been another's most likely scenario. There's debris. No, there's not. The pings were here. No, they're there. Somebody saw it. No, they couldn't have. The "facts" seem to fade in & out like the fairy lights over the bar.

[P45Mustang]

Yep....

Parked in the PRC is about as good as parked in KL gets for me.

Wake me up when they find something.