[Known Issue] Right side hydraulic pressure abnormal upon engine start since update

[Dentedend10]

Hi,

This happened twice in a row now. Cold starting the phantom in Persian Gulf or the Marianas quick missions results in abnormal hydraulic pressure on the right side. Left side is within normal. This doesn't seem to affect flight characteristics as far as I could tell, but it stayed high for the duration of the flight. On the ground, a repair was not possible to correct this.

It seems to have occurred since last patch, although I can't say for sure (not sure if I cold started the jet on these specific maps before).

Bug maybe?

[Booka42]

Also happens on other maps (Nevada and Syria) and even if you start the left engine first - it always affects the first started engine. Airstart has normal hydraulic pressure.

Edited June 7, 2024 by Booka42

[Grundar]

I'm seeing the same increase, I don't recall it being there prior to the patch.

For what it's worth, data as follows;

Caucasus Map Training mission Cold Start:

Right engine on start

- Hydraulic Pressures: Utility = 3000psi (2755 +/- 255 expected) 

- Hydraulic Pressures: PC 2 = 3900 (3000 +/- 250 expected)

- Engine Oil Pressure: 12 psi

 

Left engine on start

 - Hydraulic Pressures: Utility = 3100 psi (2755 +/- 255 expected).  Both Right and Left engine move to this position - to peer at the indicator it is at the top of the blue margin.

- Hydraulic Pressures: PC 1 = 3200 (3000 +/- 250 expected).  Right engine drops to around 3800psi.  The Left engine is on the cusp of red marker and the R) engine well exceeds it.

- Engine Oil Pressure: 12 psi.

 

Engine Parameters:

Fuel Flow

 - Right and Left: 1150 PPH

RPM

- Right 65% and Left 64%

Temp

- 340 Deg Celsius Right and Left engines

Nozzles

- Both past 3/4 open.

EDIT: No hydraulic warning lights are noted to be on at the panel

 

EDIT 2: Cold Start on Marianas map Reflected's Mission: Covey 41.  Manual Start same issue as above, Auto Start (Win + Home) same issue as well.  I start hot on the runway on a Take Off Instant Mission - Hydraulics all appear as normal ranges.

Edited June 7, 2024 by Grundar
Corrected PC 1/2 to appropriate engines

[Stickler]

I can confirm this still happens in 2.9.7.59263 MT.

A related issue may be the following:

When shutting down the right throttle as part of the Engine Shutdown checks, hydraulic pressures are completely unaffected. Only when the left engine is shut down as well do PC-1/PC-2 and utility pressure drop to zero.

Expected behaviour is PC-2 pressure dropping to zero prior to left engine shutdown (which is also a prerequisite for a proper spoiler actuator check).

Hydraulic pressure not dropping (except for a quick "jerking" loss of hydraulic pressure in all systems that quickly recovers) can also be observed when shutting down the left engine first.

Did some more testing and came up with a rather odd hydraulic-related behaviour that is best explained with the attached track. I am aware that my actions are not as per the checklist. No intentional control surface movement or actuating of any switches occurs except those described below.

Started left engine first. PC-1 initially stabilized at above 3,800 psi, Utility at 3,100 psi.

Connected air to right engine and started airflow, but never started the engine itself. PC-2 pressure rose to approximately 3,200 psi. Not sure if an RPM of roughly 21% (max 23% later on) would suffice IRL to build up hydraulic pressure above specification.

Shut down left engine. All hydraulics initially drop toward zero, then recover.

PC-2 [!] rose to 3,100 psi, PC-1 subsequently stagnated at 2,400 psi. Utility stagnated at 3,000 psi.

At about 08:04:00, the hydraulic systems experience an upward, then downward pressure jerk, with PC-2 subsequently rising back to 3,100 psi, PC-1 to 1,900 psi, Utility to 3,000 psi.

These seemingly random hydraulic fluctuations, quantitatively and qualitatively different, continued at irregular intervals until I had seen enough and ended the recording at 08:07:00. The end state was all hydraulic systems static at 3,800 psi.

As it stands, right air alone can therefore currently sustain 3,800 psi in all hydraulic systems, possibly indefinitely.

hydraulics.trk

[Zabuzard]

47 minutes ago, Stickler said:

I can confirm this still happens in 2.9.7.59263 MT.

It is a known issue and as long as you do not read anything hydraulic related in the changelog, it will still be present

[Stickler]

Since the 2.9.15.9509 changelog contains something hydraulic related ("Complete overhaul of pneudraulics system"), I thought I'd repeat the above test.

Results

Scenario 1:

1. Shutting down the right or left engine after starting hot from the ramp will not cause hydraulic pressures to decrease. Only when shutting both engines down will both hydraulics drop to zero (due to AC power being lost).
2. If external power is connected and the generators are switched to EXT ON prior to engine shutdown, hydraulic pressures remain at 3,000 psi.
3. Proceed as in Scenario 2, step 9.

Scenario 2:

1. Start in a cold jet.
2. Connect external power, so AC power is always available to power the hydraulic pressure indicators.
3. Start airflow to left engine. PC-1 and Utility stabilize at 3,000 psi with some oscillations.
4. Start left engine. No change to hydraulics.
5. Connect air to right engine and start airflow. PC-2 rises to approximately 3,000 psi.
6. Shut down left engine. No apparent effect on hydraulics.
7. Shut down right airflow. No apparent effect on hydraulics, except that fluctuations cease.
8. Hydraulics remain at about 3,000 psi indefinitely.
9. Switch off either the left or right generator. All hydraulics indicators will drop to zero. When switching the generator back on, the PC-1/2 indication will return to 3,000 psi, while the Utility indication will indicate less and less psi every time the generator is cycled. If the time with the generator in OFF has been sufficient, psi will remain at or near zero.
10. Move the control surfaces and actuate the flaps. PC-1/2 and utility pressures, respectively, will decrease until the controls cannot be actuated any more.

Notes

• The implementation has improved markedly.
• However, I still doubt an engine running at 21% (from airflow) can generate the nominal system pressure of 3,000 psi, or, based on further testing, retain pressure at approximately 2,000 psi with full demand on the control surfaces (constant stick wipeouts).
• Furthermore, I doubt that with both engines at 0% RPM, 3,000 psi can be maintained in either PC-1 or PC-2 indefinitely.
• Even if we assume this is possible, based on my understanding of the hydraulic system, after failure/shut-off of one engine, at the very least the actuation of the control surfaces should cause the hydraulic pressure of the failed/shut-down engine to drop towards zero. This is currently not the case.
• It is unclear why the Utility hydraulics indication would decrease every time AC power is removed from and reapplied to the aircraft while PC-1/2 pressures remain unaffected.

Edited Tuesday at 03:02 PM by Stickler