Eng/Bleed Air

[hassata]

Can someone provide a very brief explanation of:

 

The over-ride and motor engine switches. As I understand, after an un successful start, I'll hold the switch in override for 30 seconds without doing anything else to purge gas from the engine.

 

Over-ride I have no idea about.

 

And at which point in the start-up should I throw the Bleed Air switch? Right now I'm doing it after I check Low Oxygen and before I turn on the APU.

 

Thanks

[StrongHarm]

In my experience starting military jets IRL, the bleed air system is opened after starting the number2 engine. The bleed air system provides environmental control and resources to the aircraft (I was an environmental systems tech, so ask me if you have further questions about these systems, to include ejection seats and weapons cooling). The IGN switch, for all practical purposes, is used to do an air start. The Motor switch is used to push air through the engine without pumping fuel or igniting. This is used to get the engine to speed (26-28%) before pumping fuel and igniting, which prevents a big ball of flame out of the tail pipe. My engine start procedure:

*Start APU

*Left Engine to Motor

*At 26% push throttle over the hump and engine switch to norm

*Immediately move right engine switch to Motor

*Once left engine is fully started, right will open and start to motor

*At right engine 26% push throttle over the hump and engine switch to norm

 

Real A-10C Flash Manual

 

 

14.3. Power Plant Start and Ignition System

The power plant start and ignition system provides the initial rotation and ignition of fuel

for engine start and operation. The power plant starting system consists of an Air

Turbine Starter (ATS), two ignition systems, and a Direct Current (DC) starting fuel

pump. The method used for initiation of the power plant starting and ignition system is

determined by the aircraft configuration. Air is routed to the ATS through the starter

control valve from the aircraft bleed air system. The power plant starting system utilizes

air supplied by the APU, an external source, or an operating engine. Using APU supplied

air, the ATS is capable of motoring (rotating) the engine to 28% core rpm.

5.0. Environmental Control System

The Environmental Control System (ECS) provides a life-sustaining comfortable

environment for the pilot when the canopy is closed during preflight, flight, and

postflight operations. Bleed air is extracted from the left and/or right engine compressor

tenth-stage bleed ports or from the Auxiliary Power Unit (APU), and is supplied to the

precooler. The precooler cools the hot engine bleed air which is then divided for cabin

air and service air usage. Precooled bleed air for cabin usage is supplied to the cabin air

conditioning and cabin pressurization systems. Precooled bleed air for service usage is

supplied to the anti-g suit system, canopy and windshield defog system, rain removal

system, and windshield wash system. Service air is also supplied to the inflight refueling

purge system and the external fuel tank pressurization system. Should a total electrical

failure occur, the ECS and its components are designed to provide fail-safe operation.

System control capability will be disabled while the components maintain the position

achieved prior to the electrical failure. The ESC consists of:

Bleed Air Supply System

Bleed Air Leak Detection System

Cabin Air Conditioning System

Cabin Pressurization System

Cabin Depressurization and Ventilation System

Anti-G Suit System

Canopy and Windshield Defog System

Rain Removal System

Windshield Wash System

Windshield Deice System

Compartment Cooling System

Embedded GPS/INU (EGI) Cooling System

Fire Extinguishing System

Liquid Oxygen (LOX) System

Emergency Oxygen System

5.1. Bleed Air Supply System

The bleed air supply system supplies tenth-stage engine bleed air from either engine or

from both engines simultaneously. An onboard APU is used as an auxiliary bleed air

source. An external ground air source can be applied through the ground start transition

duct to be used as a source for bleed air supply and/or engine starting power during

ground operation. Bleed air is applied through an engine bleed air shutoff valve in each

engine nacelle to the penta-manifold, which is a central location for the merging of bleed

air from either engine, APU, or ground support equipment. The bleed air is then applied

through the penta-manifold to the engine bleed air regulator and shutoff valve where it is

regulated to 65 psi and applied to the flow limiter. The Environmental Control Unit

(ECU) converts bleed air to conditioned cabin air which is then applied through insulated

ducting along the right side of the aircraft to the cabin. For purposes of maintenance, a

red poppet-type bleed air overpressure indicator button extends to indicate that a system

overpressure condition has occurred. The button must be manually reset (depressed) when duct pressures subside.

 

 

Edited May 28, 2011 by StrongHarm

[Preacher]

Just wondering is the bleed-air system even modeled? I keep forgetting to switch it on and I never noticed any adverse effect, unlike forgetting the pitot heat.

[Shootist]

Strongarm. How important are the bleed air and whatever that other toggle is there? Your not taught to toggle them in the tutorial, or the startup procedural page I printed out a while back. Altho I've taken to flippin them anyways.

[hassata]

:thumbup:

 

Edit: Time to update the old checklist.

Edited May 28, 2011 by hassata

[Snoopy]

In real life bleed and main air are in their respective positions. One of our post and preflight inspections are to ensure bleed air is switched to bleed air and main the same....

 

The override switch on the throttle quadrant is for emergency situations only, in real life it let's the engine "overtemp" but in the sim I don't think it's modeled correctly or at all....

[sid]

I have watched many videos here of people pushing switches in many different sequencies.Can someone tell us which is the proper real method used in the real A-10?

[doright]

Bleed air does a lot of work not just spooling up the engines for starting.

Cabin pressure* and temp

Avionics cooling

Canopy seal pressure

Canopy defog

Rain removal

anti-G pants inflation

Pressurize external tanks for fuel transfer*

 

The 2 with an * I know are modelled, I'm not sure about the others.

Incidentally pulling the Fire T-handle to an engine shuts off the bleed air from that engine in addition to shutting off its' fuel.

Edited May 28, 2011 by doright

[doright]

As paulrkiii said the Bleed Air and Main Air Supply switches would usually be checked that they are on during the cockpit check before the actual startup procedure.

 

In the sim most times they are on when you are dropped in. But occasionally on some missions they aren't. I usually notice while waiting on the nav align when I do a left to right cockpit sweep of each panel to see that everything is as it should be.

 

I have watched many videos here of people pushing switches in many different sequencies.Can someone tell us which is the proper real method used in the real A-10?

[Snoopy]

I have access to all A-10 tech orders as I'm an a-10 crew dog. I am in the process of updating my checklist to mirror the A-10c-1cl (with the exception of FOUO info) and should be done by Friday next week.

[sobek]

The override switch on the throttle quadrant is for emergency situations only, in real life it let's the engine "overtemp" but in the sim I don't think it's modeled correctly or at all....

 

I'm not sure, so correct me if i'm wrong, but doesn't it just disable the temperature sensors authority in throttling the engine? I have had a temperature sensor fail on me once in the sim and the engine would stop to react to throttle changes, so i switched to override and i was again able to get some thrust. You can't get the engine past the usual RPM limit by turning override on, though.

[ErichVon]

Can someone provide a very brief explanation of:

 

The over-ride and motor engine switches. As I understand, after an un successful start, I'll hold the switch in override for 30 seconds without doing anything else to purge gas from the engine.

 

Over-ride I have no idea about.

 

And at which point in the start-up should I throw the Bleed Air switch? Right now I'm doing it after I check Low Oxygen and before I turn on the APU.

 

Thanks

 

Hi,

 

I use KonKuSSioN's "DCS:A-10C Ramp Start Checklist".

 

http://forums.eagle.ru/showthread.php?t=74072&highlight=KonKuSSioN&page=3 ; Message #22

 

https://docs.google.com/document/d/1OofEfpi9kHG_jmvT8Z3BXrgOD9AZzJrLgKAI-yF0-Q4/edit?hl=en&authkey=CI-D4mY&pli=1#

 

 

If I decide to do a full checklist, ramp start-up, I always flip both switches up before engaging engines. Bleed Air is step number 8 in the sequence. The most aft switch, "Main Air" is also part of the interior pressurized cabin environment switches that need to be on also.

 

I usually cheat and click the Right Windows key+Home key to do the 1st start-up. A lot of times in Multiplayer mode, depending on which server I am on, those two switches are not included and I manually click them up as also other stuff not included in their start-up procedure will be completed by me, before taxiing.

 

As to a 2nd start-up procedure after RTB to get repaired and a complete shut-down, I then do another start-up, either way, the cheat or the checklist of doing it, sometimes, the left engine does not spool up and will shut down. I have found, with both rudder pedal toe brakes engaged full on, as to the 1st left engine start-up, I need to add some throttle gas to get the engine to spool up to 3,000 or 4,000 rpm to get it to go. And for some reason, sometimes, ditto procedure to get the right engine up before turning off the APU generators. This has happened to me a few times this .7, #2 patch update, after RTB and starting up again. Sorry, no tracks, I just experiment and try not to complain too much and figure it out. If it is a bug, now you know.

 

(I am still a newb, but I am getting better at doing the sim, so I still question the value of me reporting oddball situations to the Testers' Team as it sometimes may be just me not doing something correctly why I do not report it.).

 

Correct start-up sequence? I do it now mostly by memory and the lighted error, malfunction, panel. I do the right side panel 1st, left side to get engines up, then after lights are on and waiting for CPU to come up I go back to the right panel and adjust my lighting. I fly every day at least one ramp cold start-up sortie since about February 2011.

 

Erich

:pilotfly:

Edited May 28, 2011 by ErichVon

[Snoopy]

When u get back from vacation I'll look in the TO and see exactly what is says about the switch.

[Phuz]

The override switch on the throttle quadrant (in this game) acts as an itt governor. If an engine is healthy, the ITT will remain more or less the same at full throttle when in either norm or ovrd. But, when an engine takes minor/moderate damage the OVRD function allows the engine to run hotter up to about 950*c on the ITT meters in order to increase it's n1/n2 output to a more normal level. When any engine gets above the redline on the ITT gauge you will get RT/LT ENG HOT warnings, but i've cruised around with those lit up for over an hour and no decrease in engine functionality [as of this patch]

 

Basically, a damaged engine needs to burn hotter in order to maintain its full power output. The OVRD switch allows the engine to do that.

Edited May 29, 2011 by Phuz

[BlueRidgeDx]

Some more investigation into how DCS actually handles the switch is necessary, but here's how it's supposed to work...

 

The ENG FUEL FLOW switches, when placed to OVRD, will bypass the ITT amplifiers in the event of an ITT amplifier failure. Under normal circumstances, the ITT amplifiers will cause fuel flow to be "trimmed" in order to limit RPM, and thus keep ITT within limits regardless of throttle position.

 

In OVRD, the ITT amplifiers no longer provide this signal, and RPM is directly controlled by throttle position. This allows the engine to be operated without regard to temperature limits.

 

The OVRD function is also useful in a single-engine scenerio where climb performance is critical. It will allow the operating engine to produce additional thrust until safe conditions can be attained.

[gear_monkey]

just my 2 cents..

 

I flew an aircraft in the airline world that has the same engines as the A-10c.

 

In our aircraft (CRJ) the engine switches engaged the electronic engine control system that always provided the most efficient fuel flow to the engines based on power lever angle, outside air temp, and a whole plethura of other sensor inputs.

 

Basically it looked at your power inputs and modified the fuel flow to be the most efficient at that time.

 

When the switches were turned off, you went to a mechanical fuel flow schedule based on power lever angle only. An HMU or hydro-mechanical unit supplied fuel to the engines.

 

You had much higher ITT's and had to really watch engine limitations but you could get "more power" from the engines. We were only allowed to operate that way when the EEC's were out of service.

[BlueRidgeDx]

Gear Monkey,

 

Yep, the switches are very similar in function to the Engine Speed Mode switches in the CRJ-200. Slightly different methods are used between the two, but in both cases the end result is an engine operating in a "coarse" fuel control mode based only on PLA.

 

Unlike the CRJ though, the A-10 doesn't have any N1 breakpoint where the N2 control mode automatically takes over (what was it, below 68% N1 or something like that?).

 

In the -700 and later we had the Engine High Power Schedule button, but that was more of a FADEC thing. We weren't allowed to use it...then again, we weren't allowed to use Flaps 1 (slats only) either.

Edited May 30, 2011 by BlueRidgeDx

[JesseJames38]

Only time you would need to use the motor switch would be to purge fuel from the aircraft engine from a failed start/hung start. During normal aircraft starting the motor switch is not needed.

 

Jesse

[BlueRidgeDx]

Yeah, the autostart system removes the need to motor the engine. Like you said, it's only really needed after a hot or hung start, or after a quickturn when ITT is still above 150deg prior to engine start.

 

Still, choosing to perform a manual start is perfectly valid, and getting the engine up to max motoring speed prior to introducing fuel does reduce the risk of start abnormalities. I think Paul mentioned that some (many?) guys at his unit do in fact motor the engine before start.

[Megagoth1702]

Guys, I really am new to the A10 and am happy that I grasped it's functionality and weapon systems. Now the motor block is waay to high for me at the moment and I didn't understand half of what I read on these 2 pages... :-/

 

I have an un-successful engine start here... I think I touched the throttle and pushed it up a bit by accident while the left engine was starting up. Now it hangs at 30% "Percent RPM" and I have no idea what to do except for getting a new plane... What do I have to do? Can you help me out?

 

Thank you a lot in advance.

[kylania]

Make sure the APU is spooled up to 100%, the APU Generator is ON and the four fuel pump switches are UP.

[Megagoth1702]

Yeah they were.

 

My re-start try routine was: turn off engines, turn off boost pumps. Wait 1 min, turn on pumps, make sure throttle is at 0%, re-try to start engines with RALT+Home etc, like in the tutorial. They still were stuck at 30% rpm. :-/

[mvsgas]

What is the ambient temp? Above 50 Celsius?

Posting a track might help us see what you are sing and maybe allow us to readily identify the problem.

[hassata]

I think someone posted to try giving it some throttle to get it to advance past 30.

[Megagoth1702]

If I throttle up I end up pulling the RPM DOWN.

 

I will post a track where I sabotage the start up procedure and then re-try, I'll show you guys in a sec...

 

EDIT: Ok, wow. I tried to sabotage it 3 times now by giving throttle before the engine was actually up, but since the ignition already happens very soon the engine still flips on.

 

I dont know how to reproduce this. If it ever happens again I will share the track for sure! I think what happens if I can't get it past 30% is that the 30% rpm are only recieved because of the APUs bleed air and there is no ignition happening. Or something, I dont know. :-(

Edited October 31, 2011 by Megagoth1702