Hydraulics Failure Question

[kontiuka]

I simulated a hydraulics failure in the F-15 and I lost air brake, wheel brake, and nose-wheel steering but aileron, flaps, elevator authority still seemed 100%. Also, my hydraulic pressure gauges still read 3000 psi.

 

Is this correct behaviour?

[JINX_1391]

Looks like it was a partial failure and/or the hydraulics system has a redundancy that takes over just for the control surfaces.

 

Some few other posts on a similar thread.

 

http://forums.eagle.ru/showthread.php?t=144639

 

I've had it happen to me after eating a friendly AIM-9; knocked out (or partial) hydraulics, HUD, all displays in the pit, and took my nose cone as a memento. Engines still worked and hydraulics to the control surfaces helped me get back to the airbase.

[kontiuka]

^

thanks

[kontiuka]

nice!

 

from today's changelog ...

 

F-15. Hydraulic failure now lead to pressure drop and loss of control

[GGTharos]

That should be a complete hydraulics failure. The F-15 has two main hydraulic systems as well as auxiliary and you need to knock out both mains at least to lose control.

 

It's not an easy feat either - if you recall the F-15 landing with one wing, that was ONE hydraulic system knocked out.

 

Similarly if your engines are out, they should provide adequate hydraulic pressure for control as long as they are windmilling at enough RPM. Get too slow and you better use that rocket-powered seat.

 

On the other hand, you could run your APU and that would get the engines spinning fast enough to give you control.

 

(FYI, the instructions in the -1 if you feel control transients or no control is to eject. Don't bother saving the plane)

 

Losing all hydraulic pressure/control in an F-15 is not easy, it takes a lot of damage.

[JazonXD]

That should be a complete hydraulics failure. The F-15 has two main hydraulic systems as well as auxiliary and you need to knock out both mains at least to lose control.

 

It's not an easy feat either - if you recall the F-15 landing with one wing, that was ONE hydraulic system knocked out.

 

Similarly if your engines are out, they should provide adequate hydraulic pressure for control as long as they are windmilling at enough RPM. Get too slow and you better use that rocket-powered seat.

 

On the other hand, you could run your APU and that would get the engines spinning fast enough to give you control.

 

(FYI, the instructions in the -1 if you feel control transients or no control is to eject. Don't bother saving the plane)

 

Losing all hydraulic pressure/control in an F-15 is not easy, it takes a lot of damage.

 

Interesting... ED has yet to implement that into the 15's model... as soon as you get hit by a missile, even if HUD and systems are still working, if the engines go out, then you lose all control no matter what. If you lost hydraulics, the control's authority decreases by a very high degree (maybe that's realistic I'm not sure).

[GGTharos]

If you only lose one hydraulic system you probably wouldn't see any control issues at all.

If you lose both engines you will get a lot of pressure drop if they're unable to windmill. Damage might cause such a situation.

[mvsgas]

F-15 hydraulics

The F-15C/D hydraulic power system consists of three

independent, interconnected systems: hydraulic Power Control (PC) 1,

hydraulic Power Control (PC) 2, and utility (UTL) hydraulic power. The

system is operated by four interchangeable plug-in type pumps attached to a

manifold on the AMAD (Airframe Mounted Accessory Drives).

The manifold enables pump removal/installation without having

to open pressure, suctions, or case drain lines. Additionally,

all system filters are interchangeable, and accessory manifolds for each

system provide a central location for filter, switches, transmitters, and check

valves. Each system has its own fluid reservoir which divides the system

into two circuits: A and B. When the systems are pressurized, fluid is routed

to both circuits. Each reservoir is equipped with reservoir level sensing

(RLS) in order to isolate a leaking circuit. In the event of a leak in the

system, the fluid in the affected system reservoir will drop. When the fluid

level drops sufficiently, circuit A is mechanically shut off. If the leak is not

in circuit A and the fluid level continues to drop, circuit B is shut off and

circuit A is reopened. Through the use of switching valves and

interconnecting lines, most subsystems can receive pressure from more than

one hydraulic system. For ground operations, all three systems can be

pressurized with a hydraulic power cart.

Power Control (PC) 1 hydraulic pump is driven by the left engine and

AMAD while Power Control (PC) 2 hydraulic pump is driven by the right

engine and AMAD. Normally, PC 1 and PC 2 power the ailerons,

stabilators, rudders, and flaps. A ground power cart connection is located in

the main landing gear wheel well for ground operation of the PC system.

The left and right utility hydraulic pumps are driven by the left and

right engines and AMADs respectively. Normally, both pumps pressurize

the UTL system simultaneously and provide pressure for all subsystems

except flight controls. In the event of failure in a PC system, utility pressure

is switched to operate flight controls. A connection inside access door 89R

enables the use of a hydraulic power cart for ground operations.

[strikeeagle]

That should be a complete hydraulics failure. The F-15 has two main hydraulic systems as well as auxiliary and you need to knock out both mains at least to lose control

 

Yes and no

It's not an easy feat either - if you recall the F-15 landing with one wing, that was ONE hydraulic system knocked out.

 

They did lose a circuit from the opposite hydraulic system as well and a circuit from the utility system. The pictures I've seen of the damage shows the MLG forward doors open indicating they had to "blow" the doors open.

 

 

On the other hand, you could run your APU and that would get the engines spinning fast enough to give you control

 

JFS

 

 

Losing all hydraulic pressure/control in an F-15 is not easy, it takes a lot of damage.

 

Thats true.

 

 

[SinusoidDelta]

FYI for those interested in discussions rather than could've/should've/would've arguments, here is what we have to work with from the -1

A failure a single hydraulic system is not considered critical because of dual systems and Reservoir level sensing incorporated into the hydraulic system design. Although not considered critical, proper treatment of the situation is warranted, as with any emergency, due to the possibility of subsequent failures which may compound the problem subsequent failures which may compound the problem. with a utility a failure, if conditions warrant, recommend in approach and arrestment. For multiple hydraulic failures the pilot must refer to the hydraulic flow diagram, this section to determine systems affected and corrective action required

A UTL A failure is the only single hydraulic failure which requires pilot action

1.if conditions warrant, recommend in approach and arrestment.

2.Refer to emergency landing gear extension procedure.

3.Emergency brake/steer handle - PULL AFTER NOSEWHEEL IS ON THE GROUND (pulling the brake above 70 knots increases the probability of blown tires.

UTL A AND PC 2 A FAILURE

1. Slow to subsonic

2 Conduct controllability check, as required.

3. if conditions warrant, recommend in approach and arrestment.

4. Refer to emergency landing gear extension procedure.

5. Emergency brake/steer handle - PULL AFTER NOSEWHEEL IS ON THE GROUND (pulling the brake above 70 knots increases the probability of blown tires.

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