PMDG B737-800 Engine Out - HELP

Profile picture for user A Spalding

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12 years 5 months

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With the recent events of the Thomsonfly B757 @ Manchester, i thought i would simulate an engine failure. My problem comes with landing the thing. I climb out on 1 engine to my desired altitude and fly the heading and course to re-establish the ILS. When I'm established on the ILS, I select flaps 15 and continue inbound on the desired speed as directed by the FMC. As the N1 increases of the active engine it creates so much Yaw that my B737 struggles to maintain the ILS even on a CAT III autoland. Any advice would be greatly appreciated. Adam
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14 years 7 months

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Yaw damper ?
Profile picture for user Deano

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No the yaw damper is there to prevent "dutch roll" which is a stability problem. Adam, the problem with flight sim is it's ability (or lack of) to "accurately" depict true flight dynamics, you should be able to maintain a desired flightpath even with 1 engine inop, the normal issues come as you slow down, basically as you approach Vmca (minimum control speed in the air) the forces needed on the rudder to keep straight increases greatly, if you go below Vmca you will run out of rudder authority. There is, or shouldn't be any issues with slowing to Vmca in planes with hydraulically actuated control surfaces but as you can imagine in a light twin such as a Seneca you will not be able to hold the aircraft straight at Vmca for longer than a minute or so. Try flying the ILS manually using the Flight Director and maintaining 5° angle of bank towards the live engine, keeping straight with rudder. I'll boot up my PMDG a bit later and test it out. It should be possible. Dean
Profile picture for user A Spalding

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12 years 5 months

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The answer i have been looking for. I'l try it out tonight also and see how i get on. I love the PMDG series and the B738, great little simulator but i worry i depend on the FMC and autopilot too much. Many Thanks for your help Adam
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No worries Adam I have tested my PMDG 738, I flew the ILS into Heathrow Rwy 27L on full manual and didn't have any issues, she actually behaved quite nicely however the yawing motion is quite bizarre, again this comes down to the flight dynamics. I found the 5° bank to the live engine helped appreciably. The key to flying this is not to get low & slow, you are really limiting your options then, because you will be near or past Vmca and you will need alot of power causing a further asymmetric force.
Profile picture for user A Spalding

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12 years 5 months

Posts: 765

Deano Many Thanks for taking the time to help me. Just out of interest, am i right in thinking that your appraoch was using flaps 15 and not 40? - Therefore creating less drag and keeping the 'live' engine's N1 lower. I also imagine that you have to be careful after touchdown and using the reverse thrusters. When using a runway such as LHR in a B738 you can be ok in just using Autobrakes. But what about BRS? I guess the use of the rudder would be important to keep the plane pointing in the right direction. I am gonna have a go tonight and see how i get one. Many Thanks once again :) Adam
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No worries Adam Naa I went for 40° of flaps to see how she reacted, she was fine as I said You are quite correct in that you need to be careful about using reverse thrust whilst in asymmetric conditions, you would normally not use reversers on the remaining engine because this will give an asymmetric force, also if you have 2 reverse thrusters this reduces your landing distance by a typical value of about 10%, so you can see they are not "that effective" anyway, the most braking actions comes from the brakes themselves (unsurprisingly), along with reverse thrust & then the spoilers. So in effect Bristol Intl should be plenty long enough to land without reversers, however, if it were a wet or slippery runway then some performance calcs may need to be done. As far as rudder goes in keeping it straight, well yes it is important, but it would be important with both engines operating, the only difference here is that as you flare you need rudder authority to "keep straight" before touchdown, again the importance of knowing Vmca is paramount, especially in crosswind conditions. But let's assume still wind conditions, you will have to have a certain amount of rudder input (usually trimmed) to counter the asymmetric force with 1 engine inop, all you would do is use "rudder as required" to straighten her up for landing and to maintain the centreline. Sorry to rabbit on. Hope this helps Dean
Profile picture for user A Spalding

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12 years 5 months

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Many Thanks for your help. I have now managed to have a successful landing, so thanks for your help. I opted for flaps 15 and therefore a higher approach speed. One thing I did try was to maintain my approach just above the glide slope. My reason for this was so that within the last 3nm of the approach I would adopt a lower nose up position (say 2.5 degrees rather than the usual 5) and therefore the N1 would be reduced as I was effectively ‘gliding'. Remembering to flare big time over the piano keys to ensure a smooth landing. Auto brakes on 2 were sufficient at Manchester and as you said in the wet I would have other factors to consider. Thankfully FS 2004 doesn’t simulate different runway conditions. Thanks for all your help Adam