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Martin Connor

Engine Start - No fuel pumps?

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I accidentally started the engines without the fuel pumps running ... successfully.  Is this properly modelled operation?  As the tanks are higher than the engines, I can imagine that this might be possible, though perhaps not above idle.

 

Same applies to the APU, but I watched a Real World video of a 737-800 startup, and sure enough, the pumps were not turned on prior to starting the APU.  That I find more odd as the APU must be at about the same level as the tanks.

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Is this properly modelled operation? 

 

Yes - as mentioned: gravity and/or suction.  Additionally, I think the APU has a built in DC (electrical) pump, but using a tank pump is recommended.

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I was trying out an APU Off start at the time.  My checklist should have included Set Parking Brake ON.  I started one off the cart, then disconnected the cart, as that is in front of one of the engines.  My start of the 2nd engine would have gone well, but I rammed the jetway.  Opps!

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I believe both the APU and engines can be suction fed.

I believe this holds  true for the 737ng also.

 

 

I started one off the cart, then disconnected the cart, as that is in front of one of the engines

 

 

usually,you would start both engines,of one source either the APU or the cart...it would put tremendous strain on one engine,if you tried starting the other with its bleed air.(esspecially if you have A/C,Pressurization etc on).

 

 

, I think the APU has a built in DC (electrical) pump, but using a tank pump is recommended.

 

yup,On ground it works when the APU is on and no AC power is available(automatically),while we are on the topic of fuel,has PMDG modelled Fuel Jettison? 

warm regards

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while we are on the topic of fuel,has PMDG modelled Fuel Jettison? 

 

It is modeled for the 747 en 777.

But it's not an option on the 737Ng. So not modeled.

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the real 737 (and btw the A320 and even some A330) does not have fuel jettison so of course it is not modeled.

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I believe this holds true for the 737ng also.

Its true for most aircraft in reality. The fuel control unit includes at least one positive delivery pump, usually two, which draw fuel from the tank. The boost pumps assist this process but are not essential to get the engines started.

 

 

usually,you would start both engines,of one source either the APU or the cart...it would put tremendous strain on one engine,if you tried starting the other with its bleed air.(esspecially if you have A/C,Pressurization etc

Cross bleed starts are normal so it's wrong to say it would put tremendous strain on the engine. Similarly with pack loads, it's recommended these are off for starting, on many aircraft types they are automatically turned off, but if left on a start should still be possible though it might be slower and hotter.

 

Unfortunately some addon developers program engine starting logic from the checklists so fuel pumps have to be on and packs have to be off to be able to start. Fortunately PMDG don't do this.

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Cross bleed starts are normal so it's wrong to say it would put tremendous strain on the engine.

 

I think my wording went caput there.Yes true crossbleed starts are normal,but do correct me if i am wrong,but it is not done very often..no?(when you have APU or power cart power that is)

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usually,you would start both engines off [...] the cart...it would put tremendous strain on one engine,if you tried starting the other with its bleed air.(esspecially if you have A/C,Pressurization etc on).

 

False.  Absolutely false.  The 777's internal logic manages the pressure automatically.  Planes have used crossbleed starts for decades.

 

In fact, it was normal procedure for Concorde.

 

 

 


while we are on the topic of fuel,has PMDG modelled Fuel Jettison? 

 

There are FUEL JETTISON buttons up on the overhead, are there not?  :wink:

 

I think my wording went caput there.Yes true crossbleed starts are normal,but do correct me if i am wrong,but it is not done very often..no?(when you have APU or power cart power that is)

 

Frequent?  No.

Infrequent because airlines advocate starting both engines off of the huffer (air start cart)?  Absolutely not.

 

Start one engine.  Remove the cart.  Push back.  [Advise ground controller, if required].  Crossbleed start the other engine.

 

Starting the engine on whatever side the huffer is on vastly increases engine ingestion risks.  An engine moving as much air as the GEs do, is able to easily take a person in.  If the person doesn't go, any articles they're wearing could be ingested (hat, glasses, bag tags, etc).  It's not worth risking FOD to an expensive engine by starting the engine on the side of the huffer.

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Kyle, you're right, but actually he was talking about the 737 not the 777. So bleed management is manual and the engines aren't huge GE's. Still, the smaller CFM is just as able to ingest ramp personnel, and sadly has done, so the same logic applies.

 

From what I've read on this forum from the people who actually do these things, starting both engines from ground air is unusual. Starting the second engine via crossbleed is the norm.

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Kyle, you're right, but actually he was talking about the 737 not the 777. So bleed management is manual and the engines aren't huge GE's. Still, the smaller CFM is just as able to ingest ramp personnel, and sadly has done, so the same logic applies.

 

I know the OP was, but I wasn't sure about 777cap, particularly because he said "this is true on the NG as well."

 

I had a CRJ pick off someone's hat once.  Definitely wasn't trying to set the GEs as a standard for picking people up.  Just noting that they were even more prone to it simply by moving that much more air.

 

 

 


From what I've read on this forum from the people who actually do these things, starting both engines from ground air is unusual. Starting the second engine via crossbleed is the norm.

 

This is correct, and that would be me.

Granted, I didn't do it from the flight deck, but as someone who's been the ground side of many a huffer start, I know how they're done:

 

Idle cart to warm

Connect hose

Once warm, (add extra hearing protection and) bring it up to operating power

Open valve when crew signals/requests

Crew starts requested engine (depends on aircraft type and SOP, but usually on the side opposite the huffer)

Crew signals disconnect

Close valve

Bring cart back to idle

Disconnect hose

Tow cart away, monitor temp, shut down once below placarded temp

 

Crew starts second engine after push using crossbleed.

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It's fascinating how an off the cuff remark can generate so much discussion.  Thanks for all your input folks.  I read somewhere - can't find now - the procedure for the cross bleed start from one engine, and it stated that there is insufficient bleed air at idle, so the running engine must be taken above idle to get about 20PSI before the other engine can be started.  Hence my remark about running into the jetway.  My increase in power caused the aircraft to swing as I had forgotten to put the parking brake on.

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I know the OP was, but I wasn't sure about 777cap, particularly because he said "this is true on the NG as well."

 

I had a CRJ pick off someone's hat once.  Definitely wasn't trying to set the GEs as a standard for picking people up.  Just noting that they were even more prone to it simply by moving that much more air.

 

 

 

 

This is correct, and that would be me.

Granted, I didn't do it from the flight deck, but as someone who's been the ground side of many a huffer start, I know how they're done:

 

Idle cart to warm

Connect hose

Once warm, (add extra hearing protection and) bring it up to operating power

Open valve when crew signals/requests

Crew starts requested engine (depends on aircraft type and SOP, but usually on the side opposite the huffer)

Crew signals disconnect

Close valve

Bring cart back to idle

Disconnect hose

Tow cart away, monitor temp, shut down once below placarded temp

 

Crew starts second engine after push using crossbleed.

Yes..i was talking about  the NG,

as for my stupid remark,i apologise.Now that i read it,it makes no sense to me either.

forget about the cfm 56's sucking in person,my grandfather saw a man being digested by a Pratt and Whitney JT8D,while doing an engine warm up.

He was just 100 feet away,when this happened..i guess that how close you can get to seeing something so gruelling.

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