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AR385
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Most Dangerous Time To Lose An Engine?

Sat May 15, 2010 8:50 am

In the discussions going on on the Civil Av. forum about the Afriquiyah crash, many posts talk about a missed approach going wrong. In that sense, it seems to me that certain circumstances are pretty silmilar to the cargo A300 that crashed on final here in MTY. There are rumors stating that this crash, the A300 one, was due to the plane losing engine no. 2 at the time of the missed approach. I also recall the crash of a learjet about 20 years ago ( I would reference it but my memory is crap these days) In that case the pilots lost an engine during final and became so engrossed on the failure that they crashed short of the runway.

If this is true, then my question is when is it the most dangerous time to loose an engine: During takeoff or during landing? What does this depend on? what are the factors involved?

Thanks in advance.
 
oly720man
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Most Dangerous Time To Lose An Engine?

Sat May 15, 2010 10:59 am

I'd say the worst time in routine operation would be

Quoting AR385 (Thread starter):
During takeoff

when you're heaviest and need as much thrust as possible.

In other circumstances we have scenarios like you mentioned and at the other extreme the famous case of the BA B747 that continued its flight from LAX to LHR on 3 engines and had to divert to MAN because of fuel issues but was otherwise routine with the SOPs.

Statistically it's probably difficult to define a scale of dangerous scenarios because there are few of each and each circumstance is probably unique.

Losing an engine somwehere like La Paz or in the mountains/valleys like Quito or Tegucigalpa will be more dangerous than somewhere flat simply because of the environment, but I'd expect the aircraft would be operated (weights) to give sufficient potential to clear obstructions.
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gatorfan
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Most Dangerous Time To Lose An Engine?

Sat May 15, 2010 12:01 pm

Quoting AR385 (Thread starter):
If this is true, then my question is when is it the most dangerous time to loose an engine:

1 second before V1.
 
Okie
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Most Dangerous Time To Lose An Engine?

Sat May 15, 2010 2:20 pm

Quoting gatorfan (Reply 2):
1 second before V1



A "contained" engine failure during take-off is probably the most practiced engine failure in the sim. A "contained" engine failure at altitude gives you the gift of time.

Worst case would be an "uncontained" failure where damage is done to integrity of the aircraft, whether it be damage to flight controls, hydraulics, electrical, damage the pressure vessel or the pressurisation system.

Okie
 
tdscanuck
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Most Dangerous Time To Lose An Engine?

Sat May 15, 2010 5:40 pm

Quoting AR385 (Thread starter):
If this is true, then my question is when is it the most dangerous time to loose an engine: During takeoff or during landing? What does this depend on? what are the factors involved?

Immediately after initiating a go-around at light weight and high flaps...if you're not careful, you could blow right through Vmca and lose the aircraft.

The case of right before V1 is also dangerous but there's usually some pad in those calculations...if you lose the engine just prior to V1 and continue, you should still safely get off the ground. Don't forget that all takeoff calculations are predicated on an engine loss at V1 (actually, just before V1 due to the reaction time buffer).

I consider the go-around case more dangerous because you don't have an equivalent V1 threshold/decision speed...if you're light and high flaps (i.e. slow) and initiate a go-around, then lose an engine, the only way to retain yaw control may be to throttle *back* on the remaining engine, which is highly counter-intuitive.

Tom.
 
DashTrash
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Most Dangerous Time To Lose An Engine?

Sat May 15, 2010 5:53 pm

Quoting tdscanuck (Reply 4):

I consider the go-around case more dangerous because you don't have an equivalent V1 threshold/decision speed...if you're light and high flaps (i.e. slow) and initiate a go-around, then lose an engine, the only way to retain yaw control may be to throttle *back* on the remaining engine, which is highly counter-intuitive.

I second this. Losing a motor at V1 isn't fun, but losing one on a missed is worse. We had that sim scenario every year where on a missed one spools up, the other quits. With flaps / gear out and a high angle of attack the airplane doesn't want to accelerate, and being close to Vmc anyway, you're in a heap of trouble. You can fly out of it, but it's not fun!
 
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DocLightning
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RE: Most Dangerous Time To Lose An Engine?

Sat May 15, 2010 9:02 pm

Quoting DashTrash (Reply 5):
You can fly out of it, but it's not fun!

What's the correct procedure?
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
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CosmicCruiser
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RE: Most Dangerous Time To Lose An Engine?

Sat May 15, 2010 9:26 pm

Quoting DashTrash (Reply 5):
and being close to Vmc anyway, you're in a heap of trouble.

Considering that V1 is lower than your Vapp are you really closer to Vmc? I guess it may depend on the jet but the procedures are the same......max power, flaps xx, positive rate, gear up, set MAP alt. In the sim we used to see a V1 cut then on the next app a miss with a second eng failure.
 
KELPkid
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RE: Most Dangerous Time To Lose An Engine?

Sat May 15, 2010 9:29 pm

Quoting gatorfan (Reply 2):
Quoting AR385 (Thread starter):
If this is true, then my question is when is it the most dangerous time to loose an engine:

1 second before V1.

Let me add to that:

At a high elevation field under conditions where Vyse is almost nil, and you are close to your single-engined serviced ceiling.

Maybe it's time to reconsider whether you really need to go flying in a multiengined aircraft under those circumstances...  
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
tdscanuck
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RE: Most Dangerous Time To Lose An Engine?

Sat May 15, 2010 9:43 pm

Quoting CosmicCruiser (Reply 7):
Quoting DashTrash (Reply 5):
and being close to Vmc anyway, you're in a heap of trouble.

Considering that V1 is lower than your Vapp are you really closer to Vmc?

V1 may not always be lower than Vapp...Vapp depends almost entirely on your landing weight and flap, while V1 depends a great deal on thrust rating, runway length and condition (and weight and flap).

Tom.
 
A342
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RE: Most Dangerous Time To Lose An Engine?

Sat May 15, 2010 9:50 pm

The worst time for an engine failure is when you have already had another engine failure before.   
Exceptions confirm the rule.
 
AR385
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RE: Most Dangerous Time To Lose An Engine?

Sun May 16, 2010 12:11 am

Quoting oly720man (Reply 1):
Losing an engine somwehere like La Paz or in the mountains/valleys

A few years ago I was based in Santa Cruz, so I flew many times in and out of La Paz on 727-200 and 727-100. The takeoff was a real show. The plane just kept going down the runway for ages. It just kept going and going, until it rotated at a very gentle angle and climbed pretty slowly. Then you would see the Illimani mountain approaching and you could not stop thinking about that EAL plane that crashed there.

Quoting gatorfan (Reply 2):
V1.
Quoting tdscanuck (Reply 4):
Vmca
Quoting CosmicCruiser (Reply 7):
Vapp
Quoting KELPkid (Reply 8):
Vyse
Quoting tdscanuck (Reply 9):
Vapp...

V1 I get. I don´t get the rest of the V´s. Can someone clarify them?
 
Sampson777
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RE: Most Dangerous Time To Lose An Engine?

Sun May 16, 2010 12:52 am

Quoting AR385 (Reply 11):
V1 I get. I don´t get the rest of the V´s. Can someone clarify them?

Vmca: The minimum airspeed at which an airborne multiengine airplane is controllable with an inoperative engine

Vapp: The safest approach and landing speed taking into account:

1. Aircraft gross weight
2. Wind condition
3. Slaps/Flats configuration
4. Aircraft status(with or without failure)
5. Icing conditions
6. Use of autothrust/autoland

Vyse: The best rate of climb with critical engine inoperative

[Edited 2010-05-15 17:53:59]

[Edited 2010-05-15 17:54:37]
Making Mom proud since 1989
 
tdscanuck
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RE: Most Dangerous Time To Lose An Engine?

Sun May 16, 2010 12:55 am

Quoting AR385 (Reply 11):
V1 I get. I don´t get the rest of the V´s. Can someone clarify them?

V1 = decision speed on takeoff.
Vmca = minimum control speed in air. Below Vmca, you don't have enough yaw authority to counter an engine out at full thrust.
Vapp = Approach speed (similar to Vref, but not usually the same value)
Vyse = Best rate-of-climb (Vy) on a single engine (se) speed

Tom.
 
dispatchguy
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RE: Most Dangerous Time To Lose An Engine?

Sun May 16, 2010 2:02 am

Quoting tdscanuck (Reply 4):
I consider the go-around case more dangerous because you don't have an equivalent V1 threshold/decision speed...if you're light and high flaps (i.e. slow) and initiate a go-around, then lose an engine, the only way to retain yaw control may be to throttle *back* on the remaining engine, which is highly counter-intuitive.

Plus, in US FARs, the only requirement for this situation is a certain climb gradient, and nothing else - no engine out go around procedure like in the takeoff case where you may have an engine-out departure.

Like at my airline, our crews are trained that the engine out departure for the landing runway is their engine out go around, for at least its better than nothing.
Nobody screws you better than an airline job!
 
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Starlionblue
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RE: Most Dangerous Time To Lose An Engine?

Sun May 16, 2010 3:02 am

Quoting tdscanuck (Reply 13):
Vmca = minimum control speed in air. Below Vmca, you don't have enough yaw authority to counter an engine out at full thrust.

So if I'm reading this right, the aircraft can be controllable at a lower thrust level on the remaining engine? I guess the problem becomes if that lower thrust allows the aircraft to stay aloft eh?
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
DashTrash
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RE: Most Dangerous Time To Lose An Engine?

Sun May 16, 2010 3:21 am

V app is also the speed you use climbing out of a rejected landing while single engine (or maybe I'm remembering this wrong....been furloughed too long).
 
CosmicCruiser
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RE: Most Dangerous Time To Lose An Engine?

Sun May 16, 2010 8:04 am

Quoting tdscanuck (Reply 9):
V1 may not always be lower than Vapp

Yeah, I know that's really true, I was speaking in general terms, I should have qualified that. On long flights Vapp may be a few knots lower than the original V1.
 
tdscanuck
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RE: Most Dangerous Time To Lose An Engine?

Sun May 16, 2010 5:27 pm

Quoting Starlionblue (Reply 15):
Quoting tdscanuck (Reply 13):
Vmca = minimum control speed in air. Below Vmca, you don't have enough yaw authority to counter an engine out at full thrust.

So if I'm reading this right, the aircraft can be controllable at a lower thrust level on the remaining engine? I guess the problem becomes if that lower thrust allows the aircraft to stay aloft eh?

Correct. In order to counter the torque of an engine out, you need an equal amount of counter-torque from the vertical fin and rudder. As you go slower, you need more rudder deflection and more sideslip to reach that torque value. At some point, you'll reach the point where the fin is developing as much force as it can and any more will stall the fin. The only way out of that situation is to speed up (difficult when climbing away on one engine with high flaps and gear hanging out) or reduce the torque (throttle back on the good engine), or both.

Tom.
 
cobra27
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RE: Most Dangerous Time To Lose An Engine?

Sun May 16, 2010 6:36 pm

Quoting A342 (Reply 10):
The worst time for an engine failure is when you have already had another engine failure before.

Ha funny and true. If others still work there is absoulutely no problem

Quoting DocLightning (Reply 6):
What's the correct procedure?

I would imagine Full power, gear up and flaps up (no the whole way up, optimum setting 5 degrees or ss) ASAP, and fly at optimum airspeed v2 or sometinh like that, later close bleed air and hydraulics and electricts when you have APU running

I have my own question, How exactly do you make full avaliable power (not that one limited for example 95 N1), press TO/GA or push the throttles full forward?Is it different for Airbus, Boeing, CRJ, Embraers?
 
DashTrash
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RE: Most Dangerous Time To Lose An Engine?

Mon May 17, 2010 1:34 am

Quoting cobra27 (Reply 19):
I have my own question, How exactly do you make full avaliable power (not that one limited for example 95 N1), press TO/GA or push the throttles full forward?Is it different for Airbus, Boeing, CRJ, Embraers?

Generally, but it depends on the airplane. A non-FADEC airplane will have to be manually set. Pushing the thrust levers to the stops will most likely toast an engine. A FADEC engine will go to max available power depending on what the setting is at the top of the TLA.
 
RaginMav
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RE: Most Dangerous Time To Lose An Engine?

Mon May 17, 2010 3:50 am

Quoting CosmicCruiser (Reply 7):
Considering that V1 is lower than your Vapp are you really closer to Vmc?

Yes, absolutely. Many aircraft have a published Vmca (Vmc air) and Vmcg (Vmc ground) to diferentiate between the the directional stability of the aircraft both with, and without, the help of rubber on the runway  
Quoting gatorfan (Reply 2):
1 second before V1.

Good point. If you continue, you're at a bit of a detriment to the 'book numbers' already. Or you can attempt a maximum-effort abort. Statistically, I wouldn't be the least bit surprised if more accidents result from attempted aborts! An Air Wisconsin captain once told me to "just go with it. You're in a jet, it's got lots of power. Just continue the takeoff and worry about it in the air". There are quite a few aborted takeoff overrun accidents I can think of, but...

Perhaps the most difficult time to maintain directional control will be a failure during rotation. The moment the nosewheel leaves the runway, you loose much of your ability to counter adverse yaw - an engine failure during rotation will leave you with only the rudder to counter the adverse yaw of the failed engine. As others have mentioned, the amount of force developed by the rudder and vertical tail is proportional to the indicated airspeed - which is lowest* at rotation.

[*and by lowest, I mean 'lowest whilst the nosewheel isn't keeping me pointed straight.']

Any experienced 737 crewmembers here? I'm sure they'll back me up on the problems of engine failure during rotation or immediately after lift off.
 
KELPkid
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RE: Most Dangerous Time To Lose An Engine?

Mon May 17, 2010 4:42 am

Quoting Starlionblue (Reply 15):


So if I'm reading this right, the aircraft can be controllable at a lower thrust level on the remaining engine? I guess the problem becomes if that lower thrust allows the aircraft to stay aloft eh?

The rule of thumb that my commercial ground school instructor taught us:

In a twin, losing one engine gets rid of 50% of the available thrust, however aircraft climb because of excess thrust (i.e. thrust above and beyond that to overcome drag for level flight). In most (GA, probably) twins, when you lose one powerplant, 80% of your excess thrust is gone. Food for thought...   Not to mention that, in an engine out situation during takeoff or climb, you are taught to put the remaining powerplant at maximum power, because a favorable outcome to an engine out depends on not flying below the surface of the Earth...

In a GA twin, you are taught, during climb, to always maintain a speed of at least Vyse (best single engine rate of climb), and maintain a healthy margin above Vmc (Minimum control airspeed, one engine inoperative) except when, of course, demonstrating single-engine aircraft control near Vmc (and you never get down to Vmc unless you have a death wish-the FAA dropped the Vmc demonstration from the practical for a good reason).
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
Mir
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RE: Most Dangerous Time To Lose An Engine?

Mon May 17, 2010 6:03 am

Quoting CosmicCruiser (Reply 7):
I guess it may depend on the jet but the procedures are the same......max power, flaps xx, positive rate, gear up, set MAP alt.

Should be something similar to that. Full power, get configured, and get the FD modes you want. Hopefully the missed approach altitude is already set from the approach.

Quoting Starlionblue (Reply 15):
So if I'm reading this right, the aircraft can be controllable at a lower thrust level on the remaining engine? I guess the problem becomes if that lower thrust allows the aircraft to stay aloft eh?

That's pretty much it. A very useful thing you can do if you're having trouble maintaining directional control on a single engine is to reduce the power on the operating engine, get things under control, and then feed the power back in slowly. But you will lose altitude in doing so, so that technique is of very limited use near the ground.

Quoting DashTrash (Reply 16):
V app is also the speed you use climbing out of a rejected landing while single engine (or maybe I'm remembering this wrong....been furloughed too long).

It's probably airplane specific - the plane I work with uses a calculated Vga, which is a bit higher than Vref (SOPs call for approaches to be flown at Vref, engine-out or not, unless you need wind corrections). We hold Vga until 1500', or higher if obstacles are an issue, then accelerate to Vyse while cleaning up the aircraft.

-Mir
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HAWK21M
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RE: Most Dangerous Time To Lose An Engine?

Mon May 17, 2010 7:33 am

Should be during T/O just near V1....Although the Aircraft would be loaded,considering one Engine out T/O,but the situation would need control by the crew considering the sudden unplanned snag.
regds
MEL.
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swiftski
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RE: Most Dangerous Time To Lose An Engine?

Mon May 17, 2010 9:16 am

Quoting tdscanuck (Reply 4):
Immediately after initiating a go-around at light weight and high flaps...if you're not careful, you could blow right through Vmca and lose the aircraft.
Quoting tdscanuck (Reply 4):
I consider the go-around case more dangerous because you don't have an equivalent V1 threshold/decision speed...if you're light and high flaps (i.e. slow) and initiate a go-around, then lose an engine, the only way to retain yaw control may be to throttle *back* on the remaining engine, which is highly counter-intuitive.

And losing upwind engine in a strong crosswind from the wrong side doesn't make things fun either.

Quoting Starlionblue (Reply 15):
So if I'm reading this right, the aircraft can be controllable at a lower thrust level on the remaining engine? I guess the problem becomes if that lower thrust allows the aircraft to stay aloft eh?

The problem is airflow over the control surfaces. If you are going slower than Vmca (or Vmcg) you will not have enough rudder authority (turning moment, vertical tailplane) to keep the a/c in balance, so you will be unable to counter the yaw of flying on one engine.

Yawing moment = asy thrust x nose -> cog arm


To hypothetically continue that, the secondary effect of yaw = roll, so you will eventually start to roll. If you're too slow, your ailerons will be more sloppy, etc etc, as will your elevator if you try to pitch up and climb away to steeply. If you pitch up too far, you approach Vs, etc. All very messy.

However.. a reduced thrust take off gives a reduced Vmcg due to the fact that in a rejected takeoff there will be less differential thrust.
 
pilotaydin
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RE: Most Dangerous Time To Lose An Engine?

Mon May 17, 2010 9:45 am

the actual V1 speed is not as important as the V1 min speed...for the A340 the min V1 speed is 130 knots....so if you lose the engine a few knots short of min V1, and you are on a contaminated runway, slippery/icy/slush...and it's a downslope....then i wish you well  
The only time there is too much fuel onboard, is when you're on fire!
 
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Starlionblue
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RE: Most Dangerous Time To Lose An Engine?

Mon May 17, 2010 1:18 pm

Quoting pilotaydin (Reply 26):
the actual V1 speed is not as important as the V1 min speed...for the A340 the min V1 speed is 130 knots....so if you lose the engine a few knots short of min V1, and you are on a contaminated runway, slippery/icy/slush...and it's a downslope....then i wish you well

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