radarcontact
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Engine # Start

Tue Dec 21, 2004 4:46 am

Hi all,

I've been on several twin-engined flights, B737, B767, B757, B777, A320, DASH8, ATR72, Piper 34 and so on. What I still don't understand is that always engine # 2 is started up first. I've even asked this to a KLM B737 captain during a cockpit flight, but he couldn't answer this question.

I've come up with an idea which might be completely wrong, but it goes like this: Since passengers are boarded via the left side of airplanes, engine # 1 is started up as last for a possible safety reason. Am I correct?

Any ideas/suggestions?
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miamiair
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RE: Engine # Start

Tue Dec 21, 2004 5:06 am

That used to be the logic behind it.
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Molon Labe - Proud member of SMASH
 
Staffan
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RE: Engine # Start

Tue Dec 21, 2004 5:06 am

Not 100% sure, but I recall it having to do with which engine that drives the pump supplying pressure to the parking brake. I could be wrong though.

Staffan
 
Venus6971
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RE: Engine # Start

Tue Dec 21, 2004 5:30 am

Which ever engine that will supply hydraulic pump pressure as soon as possible.
I would help you but it is not in the contract
 
miamiair
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RE: Engine # Start

Tue Dec 21, 2004 5:44 am

Not necessarily true. The brake has pressure in an accumulator. And there are electric pumps also. On the old jets it was #4, #3, #1 and #2, as the L/H side was the "exit."

When in doubt, follow the directions, read the manual.
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JetMechMD80
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RE: Engine # Start

Tue Dec 21, 2004 2:10 pm

I have to agree with Miamiair. Another reason also, we don't start engines at the gate unless we have an APU on MEL. We normaly start them during the push back. But if we do need a huffer, the unit is normaly parked on the left side. You wouldn't want to start the left engine, and take a chance of sucking the huffer hose into the inlet. But I still agree with Miamiair, its because the jetbridge is on the left.
"I get along great with nobody"~ Billy Idol
 
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HAWK21M
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RE: Engine # Start

Tue Dec 21, 2004 4:32 pm

I've come up with an idea which might be completely wrong, but it goes like this: Since passengers are boarded via the left side of airplanes, engine # 1 is started up as last for a possible safety reason. Am I correct?

Since the RH side is used for Servicing [Gallery,Cargo,Water,Toilet],Which is normally completed well before Startup.Hence by starting #2 first to save time,Last minute activity thru the Fwd Entry door can be accomplised safely.

On the old jets it was #4, #3, #1 and #2, as the L/H side was the "exit."

On Four Engined jets is the above sequence correct,Should there not be a stagger to avoid a pull on one wing.I would think #4,#1,#3,#2,can anyone confirm.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
miamiair
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RE: Engine # Start

Tue Dec 21, 2004 8:43 pm

The start sequence has nothing to do with the stress a power plane exerts on a wing, eccentric loading is not an issue as the design is based on a multitude of variables. And the 4312 was done so that the powerplant furthest from the fuselage was started first.
Molon Labe - Proud member of SMASH
 
BR715-A1-30
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RE: Engine # Start

Wed Dec 22, 2004 3:08 am

I've only seen engines started with #1 first. I do know that some pilots on the 727, DC-10, MD-11, and L-1011, would start #2 at the gate right before pushback and taxi on that one and while taxiing would start 1 & 3. Saves time and fuel.
Puhdiddle
 
radarcontact
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RE: Engine # Start

Wed Dec 22, 2004 4:18 am

At AMS most aircraft startup during pushback. I think that's more save than starting up while still at the gate.

Does it technically seen matter which engine is started up first with an active APU? Or is there always one specific engine which is equipped with a hydraulic pump?
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fadec
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RE: Engine # Start

Wed Dec 22, 2004 5:51 am

We would start #2 first to insure there is no hydraulic power being supplied to the steering actuators. This is primarily a safety measure should you either forget to install the steering hydraulic bypass pin on the nose gear or if the bypass failed. On Boeings the normal breaks are run off the right system, the steering is off the left. Whether the right be the #2 or #4 for the 747. 727's and 737's "B" is on the #2 engine with no #3 hyd system installed. On the DC-10 systems #1 and #3 run the breaks and steering at equally, so #2 is started first.

This was an old throw back from the days of the 737-200's which does not have a steering bypass valve. Should they accidentally leave the hydraulic interconnect closed "B" system would pressurize "A" system and nose gear would go strait, thus breaking the towbar. It is the same for the 727 with an interconnect, but there is hyd bypass installed for protection.

On normal pushbacks we would only turn on the right system electric hydraulic pump to insure we have breaks and leave the other electric pumps off until after engine start. Then we would not turn the #1 engine until the pushback driver disconnected from the aircraft and/or cleared us for #1 start. Once all was up and running then everything is turned on as normal. This procedure was followed no matter what we were driving. Whether it be an old or modern Boeing, Airbus, or Douglas. The 747 being the only odd ball, which requires the #1 hyd. system to be pressurized for main gear steering.

Once you get into the prop aircraft everything changes and I have no clue what order or reason they use.
 
TimT
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RE: Engine # Start

Wed Dec 22, 2004 12:19 pm

It used to be that the engine closest to the battery was started first, but now in the days of gas turbines using air for start that's not true. I have the most experience with the DC-10 and it really makes no difference in the order of start. BUT (there's always one of those, isn't there) many Pilots like to start #3 first because the ground crew, maintenance, push crew, etc., are usually standing on the left side to maintain visual contact with the Captain. And then to wave him off. Starting #3 first, the usual order is 3,1,2. I have learned that if the APU is a little funky, you can cheat a little and start #2 first because it has a little less air volume to recover from (shorter ducting).
The checklist I use turns on the electric hydraulic pumps and you have full pressure for brakes and steering right away.
 
sudden
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RE: Engine # Start

Wed Dec 22, 2004 6:44 pm

Hi guys,

if I'm not mistaking, here in Europe they are not even allowed to make start up at gate. (Correct me if I'm wrong).
Only exeption is when using an airstarter, naturally.

I worked 4 years at GOT as loadmaster and no.2 was always started first.
It also has to do with where the batteries are placed. Shorter travel of power, means saving the batteries. Conclution is that the pilot would start the engine most close to the battery.
(Info gathered from a friend who is a cargopilot).

Aim for the sky!
Sudden
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Silver1SWA
Crew
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RE: Engine # Start

Wed Dec 22, 2004 8:45 pm

WN starts the #2 engine first with the unusual exception that the ground crew is throwing very last minute bags in the bin in which case, to keep from interrupting the start-up/pushback procedure, they will start the #1 engine first. I believe this is rather new to the company. Until recently, the #1 engine was always started first. I can't remember the exact reason for the switch, but I swear I heard it has to do with systems hooked up and powered by the #2 engine. I should know, but I just can't think of it right now. I want to say cabin air, or A/C or something...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
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HAWK21M
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RE: Engine # Start

Thu Dec 23, 2004 2:00 am

This was an old throw back from the days of the 737-200's which does not have a steering bypass valve. Should they accidentally leave the hydraulic interconnect closed "B" system would pressurize "A" system and nose gear would go strait, thus breaking the towbar
Not until the Parking Brake is set.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
AAR90
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RE: Engine # Start

Thu Dec 23, 2004 2:05 am

I want to say cabin air, or A/C or something...

Correct. With right (#2) engine running the crew can isolate the right pneumatic system from the left system (and APU) permitting two A/C pack operation from two air sources [much more efficient maintaining cabin temp that way]. Boeing's recommended start sequence also simplifies single-engine taxi procedures as virtually all switch positions are ready for flight and the crew only needs to turn off the left A/C pack to start the left engine and turn it back on again for takeoff.
*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
fadec
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RE: Engine # Start

Thu Dec 23, 2004 5:37 am

Not until the Parking Brake is set.

We have broken tow bars with both breaks set and not set. As long as hydraulic pressure is on "A" system and there is no input from the tiller the steering will go strait.
 
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HAWK21M
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RE: Engine # Start

Thu Dec 23, 2004 6:15 pm

If System B Pumps are on + Grd Interconnect Open + Parking Brakes Selected,The A System is Pressurised.
If on Running Engines,System A Pumps selected,A System is pressurised.
The Switching off of A System Pumps only Energizes the A system Depressurising Solenoid,But a power loss can cause that solenoid to Deenergize & the Pumps to Generate pressure,Hence the Steering Disconnect valve is favoured & A pumps required to be selected off for pushback & no pushback with Engines running [ON B732s]
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
radarcontact
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RE: Engine # Start

Fri Dec 24, 2004 6:18 am

Allright, all of you thanks for reacting

Am I correct to conclude that engine nr 2 is started up first, because:

- It allows last minute actions on the left side of the aircraft
- The engine that should be started up first activates vital mechanisms such as the hydraulic system, airconditioning, cabin pressure, etc.
- It is more effective to startup the engine which makes the shortest connection to these vital mechanisms

Let me know if I missed anything

Merry X-mas!

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747Loadmaster
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RE: Engine # Start

Fri Dec 31, 2004 1:17 am

I think it is up to the company, the one I work for starts 1 2 3 4 .

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