I have been practicing some engine failure shortly after take-off, using the QRH to manage the situation.

Not easy with only one soul in the cockpit !

Things usually work out. However, this has lead to low pressure in hydraulic pumps and losing the ability to lower flaps. QRH indicates this can happen. I had to use the alternate electric system to lower slats / flaps.

My questions:

- is there a away to avoid this situation (reducing demand on the system).

- is this normal, ie should I expect this to happen each time one engine fails (in this case, engine 2).

Thanks for your expert help

 

Jean-Marc

Sorry, don't fly the NGX, but from memory I am pretty sure it has a PTU if one the EDP's fail.

 

On the bus the PTU engages automatically to provide pressure, maybe the NG requires manual action?

 

Regards

The flaps shouldn't really be an issue during an engine fail due the redundancies.

 

Can you paste the engine failure checklist you're using that mentions the flaps issue?

The system's electric pump should take over.

QRH indicates this can happen.

 

The engine failure or shutdown checklist in the QRH (pages 7.14 and 7.15) does not mention loss of hydraulic pressure as a consequence. Could you confirm this is the checklist you are using?

 

 

My questions:

- is there a away to avoid this situation (reducing demand on the system).

- is this normal, ie should I expect this to happen each time one engine fails (in this case, engine 2).

 

No, this is not normal for an engine failure without another abnormal event. Hydraulic system A and B each have one electric motor driven pump (EMDP) and one engine driven pump (EDP). An engine failure will cause the EDP in the affected side's system to stop working, but the EMDP will continue to maintain hydraulic pressure on the affected side.

 

The flaps and slats are both powered by system B, so It sounds like your number 1 EMDP was either off, overheated or you had a system B leak (qty % <40) and lost pressure that way.

 

Confirm that all the hydraulic switches pictured below are in the ON position and there are no orange LOW PRESSURE or OVERHEAT lights before you fly. Otherwise it sounds like loss of pressure from some type of system B leak.

 

Thank you for all your help.

I used the QRH 8.2 (Engine fire). QRH 13.1 indicates that some low pressure can happen if an engine is lost (but doesn't talk about loss of hydraulics - my mistake !)

I chose the option to start APU, and then selecting APU GEN on the affected side (here no 2).

It was only after a few minutes (as I was turning towards downwind) that I had the issue with hydraulics, with "low pressure" / "overheat" (by the way, I did not have any warning lights prior to takeoff).

I will redo the flight and note down the which lights came first as I can't remember exactly if I lost both the EDP and EMDP.

Thank you to Chris for such a detailed answer !

Jean-Marc

Yep, the EDP supplies about four times the amount of fluid volume as the EMDP. So when system has high demand with just the EMDP, pump output pressure is lower. Shouldn't cause loss of system pressure though.

 

Here is something else I just remembered. The 737 uses a heat exchanger in the main (wing) tanks to cycle cold fuel with hot hydraulic fluid in order to cool the associated EMDP. The minimum fuel in each tank required to do this is 1675 lbs, so if you didn't have a lot of fuel in that tank you would get an EMDP overheat and failure in addition to he loss of the EDP. Probably not relevant here, but I thought I wold just throw that out there.

 

Let us know if you can reproduce this again, I'm interested to see what happened.

 

The logic:

2 hydraulic systems + a third one for the "most important things" called Standby system

2 engine pumps, 2 electric pumps powered by the opposite engine generator

1 PTU to power system B but requires system A pressure. PTU is used only for slat.

1 Electrical motor for flap extension in alternate mode.

-flight controls can be used without hyd power

-landing gears can be extended without hyd system, could be retracted in alternate mode (with the B sys)

Rudder, wich is hyd. powered, uses A, B or Stby to move.

 

So, basically with a single failure the aircraft is still 100% operative.

If you lose an engine the electric pump is still avaiable as it is powered by the opposite engine, flaps are still avaiable (we are speaking about eng 2 loss) and, also the alternate flaps are still avaiable. The panel is on the overhead and pmdg fully modeled the system.

All hyd systems are avaiable. Running APU will only unload the remaining generator and prevent load shedding.

Also, in case of a second generator failure or a second engine failure (very bad day) the APU is still running to at least power the main systems.

PMDG correctly simulates almost all those things, also the windmilling N2 rotation wich is sufficient to power the generators and EDP by pitching down the plane.

What is not correctly simulated (limits of fsx) is the landing gear manual extension and, for a simulation choice, the manual reversion of the flight controls.

 

Stupid question, is this image above real or from the NGX? :LMAO:

 

 

Stupid question, is this image above real or from the NGX.

 

I wanted to use the NGX, but I didn't have time. This is from a very good technical site about the real aircraft, www.b737.org.uk

Alright, I went back to the cockpit and redid the flight twice. Same results.

Shortly after take-off, Eng 2 failed due to fire. Completed QRH 8.2 to shut it down. Started APU. APU Gen ON for the starboard side.

Isolation Valve back AUTO as I needed wing anti-ice.

I had a temporary "low pressure" for the EDP Eng 2 (SYS B) but it went away.

On long final (with already FLAPS 15 / gear down), as I had to use a lot more power on engine 1, I suddenly had a "low pressure / overheat" for the EMDP 1 (SYS B). At the same time, I had a "low pressure" for FLT CONTROL B", YAW DAMPER went OFF. In order to get the FLAPS 30, I used the ALT FLAPS.

At the time, I had 12,000 LBS of fuel, full load of passenger, sea level. Is the issue that I should have used a FLAPS 15 for landing

What do I do wrong ?

Jean-Marc, have you tried this without triggering an engine fire? If there is a simple engine flameout or severe damage failure use that, if not then move one of the start levers to cutoff and see if you have this issue again.

Hmmm, you shouldn't have that problem with the pump overheat. Could be a bug, but you shouldn't be landing with F30.

Jean-Marc, I believe I may have an answer to the situation you describe. The engine fire causes an EDP 2 leak and eventually loss of pressure in system B. I posted pics of the failures and the displays below.

 

I did an engine fire in which I rapidly followed the QRH in closing the thrust lever, shutting off the engine start lever, pulling engine fire switch and discharging a fire bottle, preventing exceeding the red line EGT limit. This did not produce any loss of system B quantity (97%) and pressure remained at 2800 psi throughout the flight.

 

On the second flight, I continued the climb until I reached about 8,000 ft, let the EGT exceed the red line limit and then followed the QRH. I noticed that the system B quantity steadily started to decrease until I lost EMDP due to an overheat, requiring use of ALT FLAPS to extend the flaps.

 

Definitely very thoughtful on PMDG's part and something to look out for when practicing engine fires!

Thanks for testing that out Chris, i had a feeling it might have been a situation specific to the fire failure thats why i asked him to try another form of engine failure. And of course thank you PMDG!