737 engine departs aircraft!

[calcapt]

Originally Posted by tgrayson

The issue is not what you would prefer, but what is most conduicive to safety. As long as the airplane will fly, the engine is better attached to the aircraft.

A bold statement Taylor. Can you provide any factual data to substantiate your opinion here. I absolutely disagree with your assertion and would like to see data that suggests your position is a correct one. Under certain situations me, and most of my peers, would much prefer to have the engine separate from the aircraft as it is designed to do. An engine that suffers a catastrophic failure or damage which causes severe vibration and airframe risks, has no logical reason to be hanging on a wing full of fuel and compromising other aircraft structures and systems. Yes I would be concerned about where the engine would fall, and who or what it might hurt, but my ultimate responsibility is to my own aircraft and passengers.

[flyover]

Originally Posted by tgrayson

I don't presently accept that purpose is for sudden engine stoppage, since the regs say that the structures must withstand that.

I think I see the problem. Airplanes can't read regs. And jets have had engines fall off several times since they started hanging them on pylons.

[Velocipede]

The latest on this from ISASI says the engine was fodded just after V1.

[caliginousface]

Originally Posted by Velocipede

Actually, you do. The original witness heard one loud bang and the engine departed. That's a pretty good description of a hard seizure. Your limited knowledge of jet engines and airframe systems has led you to make numerous erroneous statements on this thread.

But, by all means, go ahead and continue. Its quite amusing.

Ah come on Velo. I love your hard stances, but tgrayson is right about it being a place to learn and the snippyness kinda takes away from it.

i <3 you man

[calcapt]

Originally Posted by caliginousface

...tgrayson is right about it being a place to learn and the snippyness kinda takes away from it.

I am a late joiner to the thread but let me share a brief observation. After reading through the various posts, I was left with the feeling that Taylor (tgrayson) was very condensending to others here, bordering on disrespectful. I have no reason not to like Taylor, in fact, I have learned many things from him on this forum. I didn't receive this attitude well and neither did Velo as you can tell by his follow-on posts. Velo's point is that life doesn't always mirror what is in books and, everything that is in fact true may not always be reflected in a regulation or manual. A little more humility from some would certainly contribute to a little less "snippyness" from others. I am not speaking for Velo, but I bet he would agree.

Perhaps we all could use a little less attitude and get back to learning from each other.

[WAFlyBoy]

If jet engines are designed to separate when certain torque (or other) limitations are exceeded, then why:

o Don't they teach us that in ground school? Seems like kind of an important thing to know about, doesn't it? (I can't find a QRH item for "Engine Separation.")

o Why can't the flight crew manually jettison an engine in the event of a fire they can't control? This type of event would certainly seem to place the airframe at risk.

Even based on what I've read here, I'm not throughly convinced jet engines are designed to bail out. In my mind, a more likely solution is to design the system so that if the engine encounters an event where it absolutely will not stay attached to the airplane, it breaks off in a way that will cause the least amount of damage. But I'm not an engineer. In fact, I'm brand new at this jet-airliner thing.

It certainly would be interesting to hear a jet airplane engineer's view on this.

[Fly4Pay]

OK, from what WE were taught in every KC-135/707 class I ever took wasn't that the engine was designed to depart the aircraft if it seizes. What we WERE told was that it was designed that, in the case of uncontrolled engine fire, the engine would burn up and fall off rather than burn into the wing.

Now, obviously, I never tested that--the one engine fire I had went out when we pulled the fire switch. I DID keep some melted pieces of that engine in my flight bag for years, though!

But I think this is where this idea is coming from...

[Berkut]

Originally Posted by calcapt

I was left with the feeling that Taylor (tgrayson) was very condensending to others here, bordering on disrespectful. I have no reason not to like Taylor, in fact, I have learned many things from him on this forum. I didn't receive this attitude well and neither did Velo

I believe that when tgrayson says "show me" it's because he wants to be able to pass that information on later without having to say, "It's true, someone on the internet said so." In return, he seems to be more than happy to quote chapter and verse to back up anything he says. He's not accusing anyone of BSing; He just wants to read it for himself in the interest of educating others later.

Just my opinion, obviously.

[phoenix 23684]

Not sure if anyone has mentioned this,

You have to look back to the 60's to the 707 the idea of placing the engine in a pylon as opposed to how the comet had it inside its wing. The pylon ideas was to protect or at best minimize damage to the wing from an engine, remember that engines back in the day were not as reliable as today's engines and the comet had a few problems and not only pressurization and windows.
I can't say for certain but I could envision that Boeing's engineers design weak points on the 707 pylons in order to protect the wing and airplane. A good safety and selling point if you think about it.
I myself I'm a aero engineer and designing weak points is very common in order to minimize damage to a structure or component and to determine the life of a component.

[Doug Taylor]

Originally Posted by Fly4Pay

OK, from what WE were taught in every KC-135/707 class I ever took wasn't that the engine was designed to depart the aircraft if it seizes. What we WERE told was that it was designed that, in the case of uncontrolled engine fire, the engine would burn up and fall off rather than burn into the wing.

Now, obviously, I never tested that--the one engine fire I had went out when we pulled the fire switch. I DID keep some melted pieces of that engine in my flight bag for years, though!

But I think this is where this idea is coming from...

Ahh! Stratobladders!

[falconvalley]

There's a difference between disagreeing/debating and being condscending. Tgrayson was not the one being condescending just because he isn't the expert on this subject.

Everybody makes good points. If you look at the structure of most wing mounted jet engines, you can really appreciate what shear bolts and fuse pins are for. You have a very heavy, thrust producing machine mounted on a wing, which has to be light and aerodynamic. That is not an absolutely perfect combo, but wings are designed to handle these stresses for a limited lifespan. Nobody really wants an engine to fall off, but in the case of any type of extreme stress on that area of the wing, you would want the shear bolts to give. Otherwise, you could have quite a symphony of additional stresses on the rest of the airframe.

[tgrayson]

Originally Posted by calcapt

A bold statement Taylor. Can you provide any factual data to substantiate your opinion here. I absolutely disagree with your assertion and would like to see data that suggests your position is a correct one. Under certain situations me, and most of my peers, would much prefer to have the engine separate from the aircraft as it is designed to do.

I'm perplexed that the statement needs defending, I suppose you're accustomed to thinking from the point of view of your airplane and your passengers. However, the non-flying public, the politicians, and the trial lawyers of America would never stand for the intentional shedding of engines. The FAA knows this and has certification requirements to prevent it. One engine falling on a schoolbus full of children would cause FAA management heads to roll.

Even ignoring that, engines dropping off airplanes is hazardous even to the airplanes themselves. The 747's engine detachment took out the other engine in a few instances, apparently rendering the airplanes uncontrollable. See the El Al in Amsterdam or China Air in Taiwan. There are also other instances of dropping engines that have damaged other systems. The engine inlets apparently generate lift, tending to flip the engines backward over the wings, and gyroscopic forces throw the engine to the right. Watch out! Overall, looks like a real bad idea to drop engines, and the FAA has worked to prevent reoccurences by adding secondary support systems.

But back to the main point. Here's an interesting article about the Boeing engine detachment issue:

http://archives.seattletimes.nwsourc...&date=19930109

A pertinent quote to the discussion:

"The rules require the fuel tanks (inside the wing) and the wing to remain intact to avoid the risk of fire," said the Airbus engineer. "The Boeing and (McDonnell) Douglas approach is that, in the event of a survivable belly landing, the engine would come off the wing, hopefully cleanly.

"Our approach is that the engine would stay on the wing and slide along, again leaving the fuel tanks intact and providing a degree of protection for the fuselage."

The point in the above paragraphs is that the engine detachment philosophy has its roots in preserving the integrity of the fuel takes in the event of crash landings, not engine failure. And those quotes appear to be from an engineer, not a spokesperson.

In the words of Al Weaver, the aforementioned accident investigator, on another forum:

The regulations do not permit a design which intentionally releases a mount under engine induced loading...Meanwhile if an engine does happen to separate for any reason, then a continued airworthiness action under the regs (fix it) is appropriate to bring the design back into compliance (all previous events were addressed by this means).

His point is that any foreseeable engine failure is not expected to cause the engine to depart the aircraft. If it does, then it must be fixed. This matches the content of the regulation I posted.

Boeing aircraft have a problem with engines departing the aircraft. In almost all instances, it's due to a failure of the mounting systems due to fatigue or corrosion. However, there have been a few instances where catastrophic engine failure has been the root cause, such as the "blue ice" events where lavatory ice got sucked into the engines, or the Kalitta 747 just a few years ago. In none of these cases, though, does it appear that the engine separation was necessary to protect the aircraft.

My provisional conclusion from a few hours research is that this idea that the engines are designed to fall off after a seizure is a misinterpretation of the design criteria. Airbus engines remain attached under all circumstances, and the Boeing's probably would too with stronger engine mounts. (The Boeing fuse pins have been getting thicker over time.)

[calcapt]

See, I told you I learn things from tgrayson. Great and informative post Taylor.

I take back all the bad things I said about you.

[tgrayson]

Originally Posted by calcapt

I take back all the bad things I said about you.

All forgiven. Thank you.

The present 737 incident is still under debate. Although the FOD incident has been widely reported, those who have seen the photos of the fan blades say there is no evidence of FOD-induced damage. Others say the engine supports show sign of metal fatigue. Regardless, the operator's fleet of 737's have been grounded for engine inspections, which suggests a possible maintenance issue. And perhaps both factors are involved. No matter what the determination, it probably won't lend support to either side of the "designed to fail" discussion, since we already know that engines have sometimes separated due to FOD-induced damage.

[jtrain609]

Originally Posted by Velocipede

grayson obviously isn't qualified in jet airplanes.

Is this your ONLY argument against people?

[jtrain609]

Originally Posted by WAFlyBoy

If jet engines are designed to separate when certain torque (or other) limitations are exceeded, then why:

o Don't they teach us that in ground school? Seems like kind of an important thing to know about, doesn't it? (I can't find a QRH item for "Engine Separation.")

o Why can't the flight crew manually jettison an engine in the event of a fire they can't control? This type of event would certainly seem to place the airframe at risk.

Even based on what I've read here, I'm not throughly convinced jet engines are designed to bail out. In my mind, a more likely solution is to design the system so that if the engine encounters an event where it absolutely will not stay attached to the airplane, it breaks off in a way that will cause the least amount of damage. But I'm not an engineer. In fact, I'm brand new at this jet-airliner thing.

It certainly would be interesting to hear a jet airplane engineer's view on this.

Because my engine IS designed to burn off the aircraft in said situation, no manual jettison required. The pylon is designed to burn off in the event of an uncontained engine fire.

And that I could look up in my systems manual...if it was anywhere near me...

[Dugie8]

Originally Posted by jtrain609

Because my engine IS designed to burn off the aircraft in said situation, no manual jettison required. The pylon is designed to burn off in the event of an uncontained engine failure.

And that I could look up in my systems manual...if it was anywhere near me...

Engines are designed to burn off because of a fire, not a failure. Just want to make that clear JT, it looks like you are saying the ERJ engine will fall off if it has a fan blade burst.

[jtrain609]

You're right, I meant to write fire. Good catch, I'll go and fix that.

[tgrayson]

Originally Posted by jtrain609

Because my engine IS designed to burn off the aircraft in said situation,

A friend flying the CRJ says that the manual doesn't read this way, as he recalls. He says the manual specifies that the pylon will contain the fire, which is what the regulations require.

Would be interesting if you could post the exact language.

[jtrain609]

Originally Posted by tgrayson

A friend flying the CRJ says that the manual doesn't read this way, as he recalls. He says the manual specifies that the pylon will contain the fire, which is what the regulations require.

Would be interesting if you could post the exact language.

Good thing I fly an ERJ then eh?

Our pylon is supposed to burn through if it comes down to it. I'll go and find it in my systems manual when I get a chance, but it's in Utah and I won't be back there for another couple of weeks.

[BobDDuck]

The CRJ manual makes no mention that I can find of anything about containment. The only mention I see of the pylons in relation to fire is

The JET area consist of the jetpipe and pylon. The pylon area contains 10th-stage and 14th-stage bleed air ducting. No extinguishing protection is provided for this zone.

So I would be inclined to think they if the fire really got hot enough they would burn through. The warning system is the same as the jetpipe so there is no why to know what is burning.

[tgrayson]

Originally Posted by jtrain609

Good thing I fly an ERJ then eh?

Yeah, yeah, whatever.