hydraulics failure realism

[Guest axer]

I may be missing something here but doubt it. When you shutoff the hydraulics electrical as well as the air arent you suppose to loose the flight controls on the aircraft. I fly the PIC767 and that is fully model there plus you get the RAT which is deployed in situations like that were full hydraulic failure is encountered. With the pmdg 737 i shutdown all hydraulics and the aircraft keeps flying like nothing happens at all. Realism is set at max in fsimm. Another thing i came about while in full FMC mode flight i shut an engine off lets say right engine and there isnt any loss on the path at all . Did PMDG miss this very important part of the simulation or does the 737 have a hidden RAT type system or whatever

[Guest Andrew Potts]

The 737 doesn't have a RAT, 'cos it doesn't need one! You are having a very bad day if you lose all hydraulics, but should it happen, the flying controls are still connected by string. The controls in "manual reversion" are a bit odd - very heavy - but after a minute or so it's no big deal. Good job for electric flap operation and drop down wheels too! BUT you'll have no spoilers, nosewheel steering nor autopilots...As for not losing altitude on a single engine - what altitude / level where you at when you cut the power? At typical weights and MCT on the remaining engine, you're good for about 25,000', though it's very temperature related.

[Guest axer]

Flying at FL350 on full FMC mode shutdown one engine aircraft doesnt loose altitude nor does it loose its path either left or right keeps the same LNAV. And in reply to what you said about the full loss of hydraulics, shut all hydraulics on the aircraft and youll see theres no difference in response between hyd systems off or on.

[Guest Andrew Potts]

Axer,Well I just took a nice heavy aircraft to FL350 (M0.78) and shut an engine down. I had all automatics engaged, with the A/P in HDG SEL and ALT HOLD mode. On shutdown, the aircraft behaved correctly - slight roll and back to horizontal - followed by a decay in speed. The V/S I had to select to maintain speed was 700 fpm, about right.I then turned on the APU (this is non std, but considered a "good idea"), got out the QRH and did 7.16 "Inflight engine start". The crossbleed start worked, and I climbed back to FL350. Bizarrely, I actually felt relieved when the engine started again! (I fly these things for a living).Then I tried manual reversion (13.6). Again with all Hydraulics off, the QRH "conditions" were reflected by the sim. The only fault I could find was that I couldn't get the YD back on with system A&B flight control switches to STBY RUD. No worries, I thought - it's not really needed (though it's much harder to fly MR with no YD for real). The aircraft was just as responsive, like it would be in real life, but my yoke did not stiffen up, because there is no way PMDG can make it do that!Didn't bother trying to land it, since I don't have differential brakes on my pedals.Axer, I hope this helps you with your understanding of the 737. I fly 737 300's and 700's, and I have to say that this sim is pretty good, especially given the limitations of the PC platform.Andrew

[Guest axer]

Being a real 737 driver yourself I have a quick Q. How do you unlock the FMC from ENG OUT mode. LEts say flying again at FL350 under crz page select eng out then choose which engine, lets choose right. After 15 seconds or so VNAV operation terminates and the fmc stays locked on eng out mode. LNAV remains enabled but vnav doesnt and cant seem to figure out how to get it enabled again as like i said the fmc stays locked on eng out mode even though engines are fully operating

[Guest lbb]

Hi,This is a bug in PMDG. The U10.4 FMC should allow you to simply access these pages for reference, you can then go back to the other pages, no permanent damage done.For more info, see my previous thread under "Help, can't get out of ENG OUT page" :-)Leo Bakker

[SierraDelta 1,337]

Axer,We sort of drifted away from your claims in the original post. I've just replicated what Andrew described above and experienced the very same behaviour - loss of speed, had to descend to FL280 where I was able to maintain level flight.I'd be interested to know the conditions under which you saw the lack of reactions described in your first post.

[Guest axer]

Had a flight from ATL to BOS. Climbed to FL350 full FMC mode ap engaged on vnav and lnav. Went to the cruise page on the FMC chose eng out then chose right engine. After 15 seconds of so vnav disengages. As the previous post answered that part resolved. I went on to actually shutoff all hydraulics A and B elec and air. hydraulics went out no loss in altitude or heading everything fine there so i decided to try a few movements , aircraft had the same response as with hydraulics working no lag at all. PIC767 once hyd shutdown without RAT deployed aircraft controls degrade completely you actually notice the huge lag until RAT is deployed and you get some but with serious lag to sort of simulate what forcefeedback would in a way. Other part of this away from the hydraulics I decided to shutoff right engine completely. Cut the fuel valve on it again I had no loss on either lateral or vertical navigation. I love this aircraft as much as the PIC addon but I just think the hydraulics wasnt simulated right. To add to this is it possible to start both engines at the same time off the APU alone. Typically the PACKS have to be shutoff to get enough bleed air to feed at the most a single engine. On the dreamfleet 737 If im not mistaken APU bleed air can only manage to crank 1 engine at a time with packs off, again same as the 757

[Qavion 19]

"Cut the fuel valve on it again I had no loss on either lateral or vertical navigation. I love this aircraft as much as the PIC addon but I just think the hydraulics wasnt simulated right."Whilst the PMDG hydraulic system does have some shortcomings, I really think you are expecting too much from MSFS-based sims, "Axer" (please sign your real name at the end of your message as per forum rules). The only effective way to simulate no hydraulics flight controls (a-la 737NG manual reversion) would be to create some kind of force feedback signals to make a force feedback joystick harder to move. Unless you specifically know that the range of control column motion/ratio of pilot input to control surface output is less with no hydraulics than it is with hydraulics (are they?), then why should it bother you how the simulator behaves under such circumstances? If a sim designer made a sim less responsive (control input vs output) under such circumstances, is this realistic? (or would it just be catering to the whims of simmers who think it should be this way?)"To add to this is it possible to start both engines at the same time off the APU alone. Typically the PACKS have to be shutoff to get enough bleed air to feed at the most a single engine. On the dreamfleet 737 If im not mistaken APU bleed air can only manage to crank 1 engine at a time with packs off, again same as the 757"I think a lot of guys on the forum are making too many comparisons with Classic 737's (Dreamfleet?) and other Boeings (PIC, PS1). The NG is a new (and different) aircraft with a very powerful APU. Don't rely on PIC to make a judgement on how the real 767 behaves when it comes to duct pressures (Nor on PMDG wrt the NG). Simplifications have been made in both sims. The design of the real NG APU bleed system is such that it raises duct pressure to accommodate the bleed load (packs(in various modes), cabin temperature, engine start, etc). Classic aircraft bleed systems started out with high duct pressures (under no load) and dropped as loads were applied. Newer APU "demand type" bleed systems do the opposite...although variations have to be allowed for concerning the age/condition of the aircraft and the level of maintenance carried out (PMDG (SU2) appears to be based on a semi-worn new demand system). :-)I respectfully suggest that before you say that this and that needs to be changed, you ask the "experts" how things actually are on the real NG ;-) (and listen to what they are (repeatedly) saying)Anyway, I hope this makes sense.Cheers.Ian.

[Guest Andrew Potts]

Axer,You sound as if you have a lot of experience with the "PIC" 767 and "dreamfleet" 737. I'm afraid I cannot comment on the similarities between this product and those, since I have no experience of them.However, I am rated on the "Boeing" 737 300-900 series, and so I can say that the PMDG 737 works pretty well.I shall try one last time! If you fail an engine, both pitch and roll paths will be followed, but the speed will decay. You report this as a problem, but it is not, it is correctly modelled.In manual reversion, the response of the aircaft to a certain amount of control input is the same as when you have hydraulics, so this is correctly modelled. There should be no lag. Remember, the control surfaces are cable operated! How can there be any lag?!Trying to start two engines at the same time is just plain silly! Who cares how it behaves? You'd just never do that.Hope you are now satisfied that the sim is working OK.AndrewPSThere are a couple of simplifications in here - not relevant to the point.

[Guest Iz]

Andrew! You guys don't train the dual engine failure over there? It's a QRH checklist and we train it at least once per year as required for left-seat qualification.

[Guest Andrew Potts]

Iz - we do! NNC.7.18 in my list. Are you wondering because of the "starting 2 at once off the apu" issue? In our QRH, you start "either" engine from the apu (assuming cycling the start levers didn't do it), then do the Inflight Engine Start for the "other" engine.Our lot are keen on this I think because of the horror stories of water putting out both flames...

[Guest EricL]

>The 737 doesn't have a RAT, 'cos it doesn't need one! You are>having a very bad day if you lose all hydraulics, but should>it happen, the flying controls are still connected by string.Triple hydraulic failure is something there is no procedure listed for, because it was never envisionned it could happen. Well, it happened once on a DC10 while cruising at 37 000 ft. As part of the tail mounted engine exploded, schrapnel and debris destroyed all three systems and all three reservoirs leaked to empty.With no more control on any of the ailerons, elevator, rudder or trim, the crew still managed to land the plane. Read the full story here : http://www.airdisaster.com/eyewitness/ua232.shtmlEric.

[Guest kohenen]

Hi,I guess you are a real pilot, just got one silly questions. Are the flying controls (elevator, rudder and aieleron) still able to move by the control yoke and rudder pedal before we turn on hydraulics power? And without hydraulics, it simply means we need greater effort to move the flying controls but they still works fine?Rgds,Thomas

[Guest Andrew Potts]

Thomas, yes I am. And yes, you are correct. The poster above talking about triple hydraulic failure hasn't realised that on the 737 there are only 2 hydraulic systems, and neither are needed to move the control surfaces. When you fly with no hydraulics, it's called "manual reversion". It is a bit odd, but we do practice it in the sim and it's no real problem.