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deltafan

Enigne Failures

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When flying the 747 and setting #1 and #2 engine failures before V2, I run into many problems, even though I am following the manual's instructions. At flaps 20, 2/3 fuel load, the two engines fail just before V2. After breaking contact with the ground, the aircraft starts to slowly climb (as expected). At this point, I retract the gear and start rudder trimming away from the failed side. At full rudder trim, the plane still banks and aileron input is required. At this point the aircraft will not hold V2 and begins to descend and stall, eventually crashing into the ground.Now, I'm well below MTOW, so the 744 should fly with two engines out. How do I get it to climb and then accelerate at acceleration altitude? I've put all I can into rudder trim, plus some slight manual input, some aileron input to keep the wings level and even when trying to hold speed, it will slow down and drop. What am I doing wrong? How do I do this correctly?

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Guest Rwilson

you may need to reduce payload. I know nothing of your problem but the payload could help.sorry if this is useless info...robbie

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From my understanding, it is requirement that an aircraft must be able to fly on only half of it's engines even at MTOW. My 744 is well below MTOW.

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BTW, I've also powered down about 10% N1 on the number 4 engine, as the manual said it would help for control of the aircraft, but it doesn't help. Like I said, full rudder trim, the plane still crabs and flies sideways somewhat and I crash. I am almost sure it is a flaw with the FDE because it seems like it won't fly even under MTOW by 100,000 lbs. It just won't fly, let alone fly with only 2 engines at MTOW like it's required to do so. I don't think I'm doing anything wrong, as I have followed the manual exactly and if it still flies sideways even with full rudder input in the opposite direction, something is wrong with the plane itself.

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Guest s_L_Y_F_a

try to use aileron trim as well. And also try to activate second EEC mode. This should bust the N1 limits and give you maximum possible thrust

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Thanks dude, you are awesome! :D I didn't need to aileron trim, but switching the EECs to ALTN mode did the trick! :D OK, so I went to CON thrust after flap retraction. At this point, would I engage the AP, or do I hand fly it? Or either?

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There is no requirement for the aircraft to fly on 2 engs at MTOW. It is only certified to comply with 1 eng fail on TO. In all likely hood you would crash with 2 out at MTOW. In the real world there is no requirement to practise double engine failures on TO (only in later climb, cruise and in particular the approach) altought most of us have done one or two for "familiarisation". Getting the aircraft to Flap 1 quickly is essential and requires precise flying and very smooth control inputs.Turning the EEC's to ALTN with TO power on is not adviseable as the remaining engines you have would violently over boost and most likely result in engine damage. Rudder trim alone will not keep the aircraft straight on 2 engines. Until speed has increased you will need to hold on rudder as well as full trim. Be careful with the use of aileron trim. If you are going to use it count the number of seconds you apply it so that you can set it back to the original position when no longer needed. If not later on you will get very confused. Fly 5 degrees wing low to operative engines to assist in directional control. Remember that any excessive aileron input will also cause the associated spoilers to raise inceasing drag. Be prepared to limit thrust on the outer eng. If the AP copes leave it in but it may not as it has no rudder channel in this phase of flight (you will need to do this for it). Be prepared to disconnect it. Attempt to get to Flap 1 and V2 + 60 as this will give you the best intial 2 eng climb out to sector safe altitude and maintain controllabilty. Be aware the climb gradient, especially at high TOW's, is very poor. Expect about 200 to 500 ft per 10 nautical miles!!! Terrain will be a factor!!! If you are lucky enough to get to this point then clean up and carry out the 2 eng inop checklist. Hope this helps.CheersSteve


Cheers

Steve Hall

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I just asked a former pilot that I know. He said that the requirement was that any aircraft must be required to have the ability to perform a takeoff should half of it's powerplants are lost after V1. For example, his equipment was 757/767, so he said those craft are required to be able to fly on one engine at MTOW. He said that would then require the 747 (and now the A380) to be able to fly and climb on two engines at MTWO. Not only that, but they must also be able to climb to 200 ft. quickly enough to clear any obstacles at the end of the runway.Just as an update, I have successfully climbed out on two engines at MTOW after 2 engine failure at V2. True what you said about the rudder, had to trim and then keep manual input until airspeed increased to around 230 KIAS. Some aileron was necessary.Turning the EEC's to ALTN may result in engine damage, but at that point, I highly doubt anyone would care because of the necessity to get the plane back around to land, or have 500 people die. I'm sure engine damage would be the least of their concerns. Besides, I have got it to the point where I only need the extra boost for a fairly short amount of time. I've got it to where I go ALTN until I have obtained flaps 5 retraction, then I switch them back to NORM and reduce to CONT thrust.I have found that AP can work well with only 2 engines after accelerating past 200-210 KIAS when it can deal with rudder. I was also able to manually fly it fine. But what would the real procedure be? AP or manual? Or either?

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Update about the EEC's. They do have to remain in ALTN position until the aircraft is much lighter after fuel jettison. Even with flaps up, it still sinks and slows without the extra power, but as said above, the pilot's wouldn't care about engine damage as long as the remaining 2 engines get them back on the ground safely.

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Guest s_L_Y_F_a

I agree that in such a case you would not care about if the engines will be any good afterwards (if you make it) but rather if you can get a little more power out of them to reach a safe altitude.Nevertheless, you should consider that running an engine at 117% may lead this engine to fail also since it was never supposed to work with117% for a significant time. You should only use this "extra boost" in very critical situation and as soon as you are able to get through without the extra thrust reduce RPM so you won

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Ron I am positive that your friend is refering to twin eng aircraft only. I have been flying jets for 20 years and never heard of the 2 eng out requirement for a 4 eng aircraft that you refer to. If it was certified to do then we would be training for it and we are not. The only performance requirements on TO are for a single eng failure at V1. In this situation you will only clear the end of the runway with a minimun of 15ft (Runway limit weight and and V1). If you lost 2 engines at V1 or shortly thereafter you would not get airborne on a runway limited departure. Any altitude you get between becoming airborne and the second failure is purely a bonus and should be used to attempt to accelerate (in ground effect if need be) to retract flap. One of the big problems comes when you have to raise the gear. The doors will cause a huge amount of drag when opening and closing. Also the gear is powered by system 1 and 4. If you lose 2 engines on one side you will also lose the engine driven HYD pump and you are now relying on the air driven HYD pump on that gear to raise it. This will cause the gear to retract slower than normal and will unforunately work against you during the initial climb. I do not know how well the PMDG models 2 eng work on take off or turning off an EEC in flight at TO power. All I know is in the real world if you select the EEC's to ALTN you will not just slightly over boost if will be a major overboost. It sort of slingshots the power up. Sure if you are going to strike the ground then there is nothing to lose but before then you need to look at other options first. Those remaining 2 engs are your ONLY chance to get back safely on the ground. Do you really want to risk damaging the only only things left working for you??????? Very smooth flying is the answer. Balanced and with 5 degrees to the live engs. The autopilot on this aircraft is very good. If it is working well then use it but be prepared to disconnect. Use only the basic modes HDG SEL or HOLD and VERTSPD and monitor closely.RgdsSteve


Cheers

Steve Hall

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OK. If I were to run EEC's ALTN and only spool to about 112% N1, would an engine be able to sustain that for awhile? Because fully loaded an EEC limitation would cause the plane to crash. Both engines are failing at the same time, so I have no chance to gain altitude with 3 engines. Would an AP be able to control just after liftoff though?Or is it pretty much impossible for a fully loaded 744 to fly on only 2 engines without turning off the EEC (which in turn would lead to engine failures on the last 2 engines?Also, during climbout, if I need to avoid terrain and climbing is too slow to miss it, could I turn or would that throw the aircraft into a fairly unflyable state?

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Ron the issue here is that you already know the engines are going to fail and it appears that you have turned the EEC's off before the TO roll to anticipate the extra thrust needed. This would obviously not be done in the real world. The problem is the "slingshot" effect of turning the EEC's off when at high power settings and not so much the actual higher thrust limit. Have a look at the checklist for EEC off in the manual and you will see it says to retard thrust before turning to ALTN.I doubt the AP would be capable of controlling the aircraft just after TO. As I said in my earlier posts you need to get the wing down 5 degrees and use all the trim plus hold in rudder. Once you have sufficient speed you can ease off the bank and use the AP.You have to turn to miss terrain...no choice. It will degrade performance. Limit bank angle as much as poss but no more than 15 degrees. I will put my neck out here and say that you would not get airborne at MTOW with 2 engs failing at V1. Well you could get airborne if you yank it off but you will be coming down again and soon!!!One other thing turn off all the packs to increase avail thrust.You are delving into uncertified territory and unfortunately you have to make it up as you go along. The next time I have a sim check I will give it a try and see.CheersSteve


Cheers

Steve Hall

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