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744 Eng Fail and Vmcg

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744 Eng Fail and Vmcg

Old 3rd Jan 2021, 16:35
  #21 (permalink)  
 
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What I’m really asking is the definition of Vmcg , and does it mean increase pressure on the nose wheel if needed ( as it is Vmcg) and since it’s not written any where , should we be doing it to stay on the runway or re-evaluate our V spds
I gave the definition. Should you be increasing pressure on NW? Do so if it pleases you. . Manufacturer does tell you about crosswind takeoff/landing, EFTO and many other handling techniques. If he doesn't say it then it couldn't be making much difference. Calculation of Vspeeds? EFB does take more than half a dozen things in consideration while calculating. Airbus does progressively reduce the authority of NW steering to zero as speed increases. Airbus safety first magazine issue 11 tells you about minimum Control speed tests of A380.
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Old 3rd Jan 2021, 17:29
  #22 (permalink)  
 
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tcasblue: This discusion is about the rare occasions when the V1 is low enough to equal Vmcg. In most cases there will be a split between the Vmcg and the higher V1 so any engine failure requires the thrust be reduced to abort and therefore the handling issue goes away. I did once have an engine failure on take-off in an A340 well below Vmcg and the swing initially was very great and took us off the centreline before the thrust was reduced.
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Old 3rd Jan 2021, 18:50
  #23 (permalink)  
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From the very first lines of this thread:

Fair comment. Two ways to view the thought. Most OEMs of my reading recommend a forward stick load for takeoff in a crosswind (often with a suggestion to wash the load out as the speed increases) so an "increased" NW load of whatever magnitude is there at the failure. Concur that I can't recall a suggestion to increase loading post failure for the continued case. My take is that the line pilot, typically, has more than enough to keep him/her busy without worrying about an additional stick load input. However, the point stills remains that the thrust of the thread is background discussion to encourage thinking, rather than overt suggestions to encourage novel handling techniques.

Hopefully there is some confidence from discussing stuff like in a tech thread to reduce the surprised factor when faced with an unfamiliar combination

Therein lies a prime value of this Forum.

The larger danger, however is to substitute such in place of what the manufactures have recommended.

This is a critically important consideration. In respect of emergencies, etc., the OEM, generally, will have the preferred story for the line pilot.

meaning actual VMCG can be much greater or much less than what would be published

Hence the concern when the line pilot is faced with a min speed schedule which may put the operation somewhere near the real world, on the day, "Vmcg" (as opposed to the fixed book figure). The danger is that the typical pilot has little/no exposure to the nature of Vmcg and just how savagely handling can change in that speed region during a takeoff failure. A bit of the old forewarned is forearmed; the preference is to avoid having one's first exposure to a particular class of excitement on the fly, as it were.

Even when we did one engine inoperative takeoff training in the sim

Which is why some of us made a point of exposing newbies in the sim (even if the box is not altogether tops in fidelity) to such things for the exposure/discussion/thinking in the armchair value


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Old 3rd Jan 2021, 19:44
  #24 (permalink)  
 
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Didn’t see it mentioned above but the 744 FCOM and FCTM state that forward pressure should be applied from the start of the takeoff roll and gradually released so neutral is achieved by 80 knots IAS.
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Old 3rd Jan 2021, 19:53
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Meikleour What series of A340 did you have the failure in ? When I first flew the A340-600 I was surprised how high the min V1 was around 141 Knts from memory, having come from a 300 series with again from memory a min V1 of around 124 knots. Whenever I was in the 600 I mentally questioned the Airbus go mindedness 100 knot philosophy when it was so far below the minV1 which I guess was a Vmcg limitation.
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Old 3rd Jan 2021, 20:13
  #26 (permalink)  
 
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Originally Posted by Locked door View Post
Didn’t see it mentioned above but the 744 FCOM and FCTM state that forward pressure should be applied from the start of the takeoff roll and gradually released so neutral is achieved by 80 knots IAS.
There is a possibility that omission is due to the fact that some here have no experience on the 747-400? Or the dubious effectiveness of it’s nose wheel? Certainly when compared to the power of it’s rudder.

If we’re talking about ‘real world’ situations, the very last thing I wish to be discussing with a colleague (even in advance of any potential event) is the notion of attempting something totally non standard picked up after reading an internet forum. Where some bright spark thought it was a wizard wheeze!

If it’s considered ‘best practice’ then ‘our people’ should get in touch with ‘their people’ (the manufacturer) and get it written in the manuals!

Anything else is well off piste.
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Old 4th Jan 2021, 09:19
  #27 (permalink)  
 
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Out of here: I have just looked at my old manuals and for the -300 Vmcg was 126.5kts (-600 Vmcg was 136.5kts ) My incident was on a -300 TOGA departure.

With a min V1 driven by Vmcg it is hard to see a situation where TOGA is being used therefore the handling issue should be less critical in practice since less than TOGA thrust is usually being used. That is the very reason why Airbus certify Derated Take-off Performance to allow slippery runway ops with low V1s.

I do not think that Airbus are talking about engine failure when they talk about being "go minded" above 100kts.
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Old 4th Jan 2021, 09:55
  #28 (permalink)  
 
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Meikleor: Thanks very much, sure I get the 100kts thing is just an arbitrary number not intended for engine failure more a kinetic energy V squared thing for other failures. When operating both types I was very aware of the performance differences and as JT has mentioned I think it is good practice to sit in the armchair/bath/bar and think these things through. Interestingly my operator at the time did not utilise De-Rated power just Flex up to isa+60 (600) ie max flex 75 at sea level corresponding to a 40% power reduction. I don’t suppose you remember roughly what speed you had your failure at in the 300?
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Old 4th Jan 2021, 11:42
  #29 (permalink)  
 
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I do not think that Airbus are talking about engine failure when they talk about being "go minded" above 100kts.
Definitely not! Being Go minded is not a blanket clearance to just carry on. FCTM specifically mentions five categories of failures which call for reject takeoff even after 100kts. The second category is sudden loss of thrust also in the fifth category it gives five failures for which to reject the second is engine failure. To be go minded the aircraft must be controllable. A320 VMCG is 109kts and beyond.

Last edited by vilas; 4th Jan 2021 at 12:30.
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Old 4th Jan 2021, 13:03
  #30 (permalink)  
 
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Originally Posted by vilas View Post
Definitely not! Being Go minded is not a blanket clearance to just carry on. FCTM specifically mentions five categories of failures which call for reject takeoff even after 100kts. The second category is sudden loss of thrust also in the fifth category it gives five failures for which to reject the second is engine failure. To be go minded the aircraft must be controllable. A320 VMCG is 109kts and beyond.
I sure don't understand this. So many accidents due to aborts at 100+ kts on the big iron and so few cases where the situation was seriously in doubt to justify abort above 100 kts. Sure the pilot must make a decision based on his perceptions, but I do think that it's unwise to issue a blanket piece of advice of when to go and not to go
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Old 4th Jan 2021, 14:32
  #31 (permalink)  
 
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The reasoning for the advice to be 'biased' as 'go' minded at high speeds stemmed from the TakeOff Training Safety Guide.
Perceptions are subject to error; knowing beyond reasonable doubt grows with training and experience (hopefully always in the simulator).

A simplified view:-
https://www.flightsafetyaustralia.co...0/think-quick/
for info:-
https://flightsafety.org/files/RERR/...gSafetyAid.pdf

https://www.skybrary.aero/bookshelf/books/921.pdf

https://www.skybrary.aero/bookshelf/books/197.pdf

https://www.skybrary.aero/index.php/...off_(OGHFA_SE))

https://www.skybrary.aero/bookshelf/books/1326.pdf

Last edited by safetypee; 5th Jan 2021 at 07:47. Reason: Link repair, add
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Old 4th Jan 2021, 21:56
  #32 (permalink)  
 
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Out Of Here: Sorry, it was a long time ago - it was certainly before the 100kts call which we also used as an ASI confidence check and therefore my view was outside at the time! An interesting sidestory about this was although it was the failure of some turbine blades out the back of the engine which resulted in a massive engine surge and an EGT in excess of 1,000C - when we came to a halt there was NO appropriate ECAM displayed!! This initially flumoxed the F/O since it was his first line trip and he never had thought that he might have to do the ECAM items from memory! Perhaps the differences in Vmcg may have been because of different engine ratings?
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Old 5th Jan 2021, 05:55
  #33 (permalink)  
 
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Meikleour: A very interesting experience, thanks for sharing. On the first sector side of things I once had a reverser partially deploy on a 340 at rotate, it turned out to be a primary lock failure but the secondary caught it.
Again it was the F/O’s very first line sector albeit a short one! Apologies for thread drift.
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Old 5th Jan 2021, 12:10
  #34 (permalink)  
 
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Originally Posted by lomapaseo View Post
I sure don't understand this. So many accidents due to aborts at 100+ kts on the big iron and so few cases where the situation was seriously in doubt to justify abort above 100 kts. Sure the pilot must make a decision based on his perceptions, but I do think that it's unwise to issue a blanket piece of advice of when to go and not to go
From Airbus Safety First:
  • What are the operational implications of not respecting V1?
Supposedly, there are two different ways of “disrespecting” the V1 speed criteria:

1 - The crew decides to continue take-off while an engine failure occurred before V1.

Standard procedures encourage the crew to reject take-off if an engine fails before V1. If take-off is continued despite this recommendation, then the aircraft can potentially exit the runway laterally, or be unable to take-off before the end of the runway.

2 - An RTO is initiated above V1.

Virtually, any take-off can be “successfully” rejected, on the proviso that the reject is initiated early enough and is conducted properly. In this respect, the crew must always be prepared to make a GO/ NO GO decision prior to the aircraft reaching V1.

Doing otherwise exposes the aircraft to an unsafe situation where there either may not be enough runway left to successfully stop the aircraft - therefore resulting in a longitudinal runway excursion-, or maximum brake energy is exceeded and brakes catch fire.

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Old 5th Jan 2021, 14:26
  #35 (permalink)  
 
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Originally Posted by vilas View Post
From Airbus Safety First:
  • What are the operational implications of not respecting V1?
Supposedly, there are two different ways of “disrespecting” the V1 speed criteria:

1 - The crew decides to continue take-off while an engine failure occurred before V1.

Standard procedures encourage the crew to reject take-off if an engine fails before V1. If take-off is continued despite this recommendation, then the aircraft can potentially exit the runway laterally, or be unable to take-off before the end of the runway.

2 - An RTO is initiated above V1.

Virtually, any take-off can be “successfully” rejected, on the proviso that the reject is initiated early enough and is conducted properly. In this respect, the crew must always be prepared to make a GO/ NO GO decision prior to the aircraft reaching V1.

Doing otherwise exposes the aircraft to an unsafe situation where there either may not be enough runway left to successfully stop the aircraft - therefore resulting in a longitudinal runway excursion-, or maximum brake energy is exceeded and brakes catch fire.
Thank you very much, now may we have a B747 procedure covering the same situations?
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Old 5th Jan 2021, 16:14
  #36 (permalink)  
 
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Recollections of the B744.

One of the company's 744s at a slowish speed (well below 80kts), but at max power, rapidly lost the power of one of the outboards. As the aircraft swung violently into the dead engine, the crew in quicktime idled the throttles, stood on the brakes and pushed hard on the nose wheel steering in the opposite direction. Stopped 3 feet from the grass only because of the instant response from the crew.
So, until 80kts when the rudder has some control over direction, we kept a slight nose down pressure on the stick to keep the nose wheel reasonably firm on the ground, and of course, if required a little into-wind aileron.
Personal technique: Most of my experience with the 744 was either long haul or ultra long haul, therefore trundling down the runway, with the speed increasing towards V1, thoughts of abort are always present. However, as the speed approaches V1 (eventually), about 5kts prior, I used to uncurl my fingers slowly from around the throttles and move my thumb away from the disconnect. Hand still in contact with the top of the throttles until V1, them fully smoothly remove. WE GO FLY?? Not quite yet, as a few more long seconds are required until rotate, and then select the attitude, and hopefully claw into the lower atmosphere!!
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Old 6th Jan 2021, 03:00
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Originally Posted by twothree View Post
Recollections of the B744.

One of the company's 744s at a slowish speed (well below 80kts), but at max power, rapidly lost the power of one of the outboards. As the aircraft swung violently into the dead engine, the crew in quicktime idled the throttles, stood on the brakes and pushed hard on the nose wheel steering in the opposite direction. Stopped 3 feet from the grass only because of the instant response from the crew.
So, until 80kts when the rudder has some control over direction, we kept a slight nose down pressure on the stick to keep the nose wheel reasonably firm on the ground, and of course, if required a little into-wind aileron.
Personal technique: Most of my experience with the 744 was either long haul or ultra long haul, therefore trundling down the runway, with the speed increasing towards V1, thoughts of abort are always present. However, as the speed approaches V1 (eventually), about 5kts prior, I used to uncurl my fingers slowly from around the throttles and move my thumb away from the disconnect. Hand still in contact with the top of the throttles until V1, them fully smoothly remove. WE GO FLY?? Not quite yet, as a few more long seconds are required until rotate, and then select the attitude, and hopefully claw into the lower atmosphere!!
Low speed reject requires simultaneous application of full rudder, differential braking and thrust reduction all the way into reverse(at least on Airbus twins) which turns the aircraft away from the failed side. Those who takeoff with feet up on the rudder peddles and use the steer with heel and brake with tow technique find it easy to control the swing. Those who takeoff with heels on ground may struggle to get the foot up for differential braking. In 747 classic the nose wheel is not connected to the rudders and in the simulator this exercise with runway wet was challenging but still it was manageable if feet were up.

Last edited by vilas; 6th Jan 2021 at 08:25.
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Old 6th Jan 2021, 05:33
  #38 (permalink)  

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Originally Posted by vilas View Post
Low speed reject requires simultaneous application of full rudder, differential braking and thrust reduction all the way into reverse(at least on Airbus twins) which turns the aircraft to the failed side.
(airbus twin hijack) More specifically into the grass towards the failed side. The FCTM explains the proper sequence. (/hijack)

[* vilas quoting the OEM guidance non-explicitly? Welcome 2021, until today and I thought the previous was the bad one. Not even a full week, fluff!]
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Old 6th Jan 2021, 08:18
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Originally Posted by FlightDetent View Post
(airbus twin hijack) More specifically into the grass towards the failed side. The FCTM explains the proper sequence. (/hijack)

[* vilas quoting the OEM guidance non-explicitly? Welcome 2021, until today and I thought the previous was the bad one. Not even a full week, fluff!]
Thank you for correcting. Actually away from failed side. Corrected the previous post also. Getting rusty, though just had a LVO sim session.
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Old 6th Jan 2021, 21:26
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Originally Posted by vilas View Post
Low speed reject requires simultaneous application of full rudder, differential braking and thrust reduction all the way into reverse(at least on Airbus twins) which turns the aircraft away from the failed side. Those who takeoff with feet up on the rudder peddles and use the steer with heel and brake with tow technique find it easy to control the swing. Those who takeoff with heels on ground may struggle to get the foot up for differential braking. In 747 classic the nose wheel is not connected to the rudders and in the simulator this exercise with runway wet was challenging but still it was manageable if feet were up.

This again,

Are there any operators out there who encourage this dubious practice ?

Heels should be on the floor for take off and on landing until initiating manual braking
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