BR715-A1-30
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Battery VS. APU Engine Start?

Fri Nov 02, 2007 4:42 pm

Hello Everyone.

I have flown on board many aircraft, from DC9s to 717s to 737s to ERJs to CRJs to ARJ-85s. And I was wondering, which aircraft out there do not use the APU for engine start and instead use an electric starter? The Cessna Citation, I can tell has an electric starter, as you can hear it click over. I know the ARJ-85 has an APU, but is it used to start engines?

here are a few examples. Please help me find some answers..





What say you? (Other than "Cool Videos")
Puhdiddle
 
oldtimer
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RE: Battery VS. APU Engine Start?

Fri Nov 02, 2007 10:47 pm

Most aircraft use air start off the APU, or in the event the APU is U/S, they use a ground air supply. The B747 would require two ground units but does normally start off the APU. The Bae 146/RJ series use electric starters using the APU or an external power supply. Some aircraft were fitted with a mod enabling the aircraft to start off internal batteries but it did cane the batteries. On early 146's they suffered badly with starter motor shaft failures due to the high torque on initial start attempt and a mod was introduced to enable a two stage soft start to save shaft wear.
ll Boeing a/c prior to 787 (jet powered) have air starters. The only pure jets I can remember with electric start were the Comets and Caravelles.
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Oldtimer
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boeing767mech
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 1:26 am

Quoting Oldtimer (Reply 1):
The B747 would require two ground units but does normally start off the APU.

Interesting thing is the 757 with RB211-535E's has to have 3 Start carts for a not APU start.

David
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roseflyer
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 4:58 am

The 787 will be rather unique in that it will have electric starters which are actually the generators. They aren't called IDGs (Integrated Drive Generators) because they have the capability of starting the engines. The amount of electrical power during start up will put a big demand on the APU, but unlike all the other Boeing jets, it will be exclusively electrical power as there is not bleed air on the plane to be used for starting the engines.
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BR715-A1-30
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 5:31 am

IIRC, the Boeing 717 required 2 start carts at first. I think that happened until either the MA-1A was brought out, or some kind of MOD to the APU was brought out.. Correct me if I am wrong.

[Edited 2007-11-02 22:38:22]
Puhdiddle
 
Tristarsteve
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 10:35 am

Quoting Boeing767mech (Reply 2):
Interesting thing is the 757 with RB211-535E's has to have 3 Start carts for a not APU start.

It is not the number of carts, it is the mass flow of air.
I have started a RB211-535 with a single hose, but the system had a very high mass flow.
We have a very good ( and very old) air start cart here, and its 2 hoses have started evrything, even big engines like GE90 or Trent 800.
Anyway how do you connect three carts to a B757, there are only two connections?
 
Goldenshield
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 2:25 pm

Most all turboprop engines are started electrically via a starter/generator with power from the APU (if equipped) or a GPU.

From what I've read, the Shorts 360 was started from an internal battery.
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FlyASAGuy2005
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 3:28 pm

Quoting Goldenshield (Reply 6):
Most all turboprop engines are started electrically via a starter/generator with power from the APU (if equipped) or a GPU.

 checkmark 

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lmml 14/32
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 3:38 pm

I beleive even the 777 can start on electric power. Can anybody confirm this pls?
 
boeing767mech
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 3:54 pm

Quoting LMML 14/32 (Reply 8):
I beleive even the 777 can start on electric power. Can anybody confirm this pls?

The engine starters on the engines are pneumatic, so no electric start, the APU has both electric and pneumatic starters.

David
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dl757md
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 4:17 pm

Quoting RoseFlyer (Reply 3):
They aren't called IDGs (Integrated Drive Generators) because they have the capability of starting the engines.

Not exactly. The IDG is so called because it combines a CSD and a generator into one unit. The starter generators on the 787 will not have a CSD because they will not produce clean 400Hz power. They will produce wild voltage at varying frequency which will then be conditioned by 'power stations' located throughout the airplane.

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BAE146QT
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 5:00 pm

Apropos of those videos, I would love to know why someone thought it was a good idea to hold a video camera less than a foot away from - or possibly at the lip of - the intake of the BAe/RJ in the first clip, (as is clear from the first 3 seconds of it).

Don't get me wrong - I'm not a Health and Safety wonk - but that sort of behaviour is a little Darwinian in my non-professional opinion.

Even if it's not the most dangerous thing to do around an aircraft, it shows a certain amount of contempt for risk.
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troubleshooter
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 5:44 pm

I prefer engines with a pneumatically operated starter. Electrically operated starter motors have a very short operation time compared with pneumatic starters. Performing engine ground runs and motoring checks is more "relaxed" when you have a pneumatic start system.
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dl757md
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 5:45 pm

Quoting BAe146QT (Reply 11):
I would love to know why someone thought it was a good idea to hold a video camera less than a foot away from - or possibly at the lip of - the intake of the BAe/RJ in the first clip, (as is clear from the first 3 seconds of it).

If you listen carefully to the audio you can tell that the camera moves away from the intake as fuel and ignition comes on. Prior to that there is no real danger of ingestion. It wouldn't be a good idea to stick your hand in the fan but you'd be putting it rather than it being sucked in. I would say that the video showed that the videographer had a realistic sense of situational awareness and never put himself in danger.

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BAE146QT
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 6:18 pm

Quoting Dl757md (Reply 13):
I would say that the video showed that the videographer had a realistic sense of situational awareness and never put himself in danger.

I hope I didn't sound like, "Stay Away From Jet Engines Or You Will Die".

I guess it's the way he bolted when the motor spun up proper.You say it means he had a good appreciation of the risk. To me it made it look like he was running away from a bottle rocket. I don't work with turbines on a day-to-day basis, (not ones that are more that 6" in diameter, anyway!), so I will defer to your analysis.  Smile
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HAWK21M
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 6:19 pm

Quoting Boeing767mech (Reply 2):
Interesting thing is the 757 with RB211-535E's has to have 3 Start carts for a not APU start.

Thats for High OAT conditions.We use Two carts satisfactory.Its the Volume that matters because of the Triple spool configuration of the RB211-535.

Quoting Tristarsteve (Reply 5):
Anyway how do you connect three carts to a B757, there are only two connections?

You use Two pneumatic Jet start units.

regds
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tdscanuck
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RE: Battery VS. APU Engine Start?

Sat Nov 03, 2007 10:47 pm

Quoting BAe146QT (Reply 14):

I guess it's the way he bolted when the motor spun up proper.You say it means he had a good appreciation of the risk. To me it made it look like he was running away from a bottle rocket. I don't work with turbines on a day-to-day basis, (not ones that are more that 6" in diameter, anyway!), so I will defer to your analysis.

Being in front of a running jet is not generally healthy, but if you're got enough experience to know where the danger zone is without taking your eyes off your camera, no big deal.

The problem with the suction danger around jets is that there is no warning. Since the suction increases extremely quickly as you approach, your first sign that you've gone too far is that you're heading for the fan with nothing to stop you.

Tom.
 
boeing767mech
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RE: Battery VS. APU Engine Start?

Sun Nov 04, 2007 1:25 pm

seeing that video reminds me when we used to do coke washes on the DC10's. Was alittle disturbing when they strap you to a truck wear a harness, while the engine is running at Flight Idie, and your holding a 10 foot wand trying to aim it at the spinner to shot the coke in the core engine and not waste it in the bypass area.

Oh yeah and all this on the night shift. But does make a cool light show seeing the sparks fly out the back.

David
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boeing767mech
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RE: Battery VS. APU Engine Start?

Sun Nov 04, 2007 1:31 pm

Quoting Tristarsteve (Reply 5):
Anyway how do you connect three carts to a B757, there are only two connections?

Our 757's have 3 pnuematic connections on the manifold. two on the L/h side of the isol valve and one o the R/H side of the aircraft. I look in a pilots ops manual and they need 3 carts for hot and high fields in South America where the field elevation is over 10K.

David
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jetstar
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RE: Battery VS. APU Engine Start?

Sun Nov 04, 2007 10:23 pm

Almost all corporate jets up to the Gulfstream size have electric starters, usually a starter/generator combo. Gulfstreams and up used air starters.

On larger jet engines the air starter can provide the high torque needed to turn the engine but at a much lighter weight than an electric starter would weigh.

On corporate jets with starter/generators, the power is taken from the battery, not the APU because of the high amperage needed. A lot of the smaller corporate jets do not even have APU’s.

On the Lockheed JetStar, electric starter power was provided by 2 nicad batteries and all the APU or engine starter/generators did was charge the battery. The APU and each engine had a 300 amp starter/generator, but when the starter switch was pressed, the APU and any starter/generator on line would be disconnected until the starter switch was released. This was to prevent damage to the aircraft wires. The engine starter/generators did not have any circuit protection but the APU which had the same starter/generator that the engines had was protected by a 300 amp slow blow fuse.

The Jetstar did not come from the factory with an APU, they were installed as an aftermarket item by the completion centers on most but not all JetStars, so the pilots had to manually switch off the generator before engine start or it would blow the APU starter/generator fuse. And every JetStar carried a few spare fuses because sooner or later a pilot would forget to switch off the generator before battery starting and blow the fuse.

Some JetStars were wired with a bypass so the APU generator did not have to be manually shut off when starting off of the batteries.

At home base and sometimes on the road we would use an external electric start cart instead of the batteries, these carts had a large auto engine on them turning a generator. They are like the Hobart units welders use on their trucks for remote arc welding. Some were self powered and others had to be towed by a tug. One of the older towed start carts at our home base FBO, the generator was powered by a Chrysler Hemi head V8, that how powerful they were. When starting off of a start cart, when the pilot initially pressed the start switch, the draw on the start cart generator was enough to cause the engine RPM to drop.

One time the connector plug was worn and as the pilots were starting the 3rd engine, the plug got so hot it melted and started to arc and burn. Fortunately I was standing next to the start cart and immediately pulled the plug out. We shut down the engines and I did an inspection and found no damage to the airplane, so they restarted the engines using the batteries. Couldn’t say the same thing for the start cart, the entire plug and wires had to be changed.
 
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Jetlagged
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RE: Battery VS. APU Engine Start?

Tue Nov 06, 2007 12:55 am

Quoting RoseFlyer (Reply 3):
The 787 will be rather unique in that it will have electric starters which are actually the generators. They aren't called IDGs (Integrated Drive Generators) because they have the capability of starting the engines.

Not really a new idea. Starter/generators have been used before. Of course those on the 787 are very much larger!
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freshlove1
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RE: Battery VS. APU Engine Start?

Tue Nov 06, 2007 2:18 am

Quoting Goldenshield (Reply 6):
Most all turboprop engines are started electrically via a starter/generator with power from the APU (if equipped) or a GPU.

From what I've read, the Shorts 360 was started from an internal battery.

Beech 1900D....Battery start unless it is really, really cold then you got to hook up the ground power to give it a little extra juice to get going.
 
kstatepilot
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RE: Battery VS. APU Engine Start?

Tue Nov 06, 2007 3:39 am

Quoting Goldenshield (Reply 6):
From what I've read, the Shorts 360 was started from an internal battery.

All the 330/360's are normally started from the battery. The aircraft actually have 2 batts, the main one and then one that was only used to "assist" in starting the engines.

The only place I have used a GPU when starting the Shorts was at the UPS cargo ramp in SDF. This made for a lot cooler starts. However the GPU's are broken/run down quite a bit, so alot of the time we used the batt's.
 
EMBQA
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RE: Battery VS. APU Engine Start?

Tue Nov 06, 2007 3:45 am

Quoting Goldenshield (Reply 6):
Most all turboprop engines are started electrically via a starter/generator with power from the APU

None that I can think of.....as far as bigger regional turboprops. Most all that I can think of are started from batteries....as many don't even have APU's....and those that do have APU's provide cabin air only.

[Edited 2007-11-05 19:54:13]
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airtran737
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RE: Battery VS. APU Engine Start?

Tue Nov 06, 2007 6:40 am

Quoting BR715-A1-30 (Reply 4):
IIRC, the Boeing 717 required 2 start carts at first. I think that happened until either the MA-1A was brought out, or some kind of MOD to the APU was brought out.. Correct me if I am wrong.

When the 717 first came on line at FL they all flew with a Y coupler so that two air-start units could be hooked up to it. After a while it was decided that one air-start cart would be good enough, and the company pulled the Y couplers off the planes. The BR-715 only needs a sustained 30 p.s.i. to crank the engine, which is not that much.
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doug_or
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RE: Battery VS. APU Engine Start?

Tue Nov 06, 2007 9:28 am

Quoting EMBQA (Reply 23):
.and those that do have APU's provide cabin air only.

?

What types have cabin air only APUs?
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HAWK21M
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RE: Battery VS. APU Engine Start?

Sat Nov 10, 2007 7:53 am

The ATP Turboprop starts using an electric starter as it does not have an APU.
regds
MEL
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