Engines start sequence (3-4-2-1): why?

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ilya1502
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Engines start sequence (3-4-2-1): why?

Post by ilya1502 »

I was pretty much surprised to know that this was not specific to Connie, but the same start sequence is outlined for DC-6, too. I understand why from the right side, but why from #3? Why not from #4?

AviationAtWar
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Re: Engines start sequence (3-4-2-1): why?

Post by AviationAtWar »

Current operators of four engine aircraft will tell you it's for safety. If you had an outboard already running, were starting an inboard and a fire started then your firegaurd has to move past the running outboard to get to the inboard.

flapman
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Re: Engines start sequence (3-4-2-1): why?

Post by flapman »

Quick internet search discusses topics such as what equipment is provided by which engine (hydro pumps first). It actually sounds like there's quite a bit of variety, but 3-4-2-1 is the most common. My justification is that the passenger exit is on the left side, and starting an inboard first is safer for ground personnel (if they are approaching the aircraft from the sides...more airplane structure they have to walk past before they encounter a spinning propeller). Hopefully by the time the inboard engine is started, crews will use appropriate caution to avoid the outboard engine as well.

When I flew the Piper PA-44-180 Seminole, we always started #1 first, because we exited the aircraft on the right side. In the PMDG JS4100, I also start #1 first (despite the fact the exit is on the let side) because the GPU is connected on the right side, and the ramp crew has to disconnect the plug from behind the #2 engine (no APU).
Last edited by flapman on 22 Nov 2017, 14:27, edited 1 time in total.

alan CXA651
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Re: Engines start sequence (3-4-2-1): why?

Post by alan CXA651 »

Hi.
Not all aircraft start in this sequence , the B17 is one that as a start of 3,4,1,2 , because of getting the batts recharged which happen to be in engines 3 , 4 and 1 , and thats the sequence of gens comming on line , this is also why the batt switches are labelled 1 , 3 , 4 .
Also depending on the temps at the airport , the connie and b377 will start the outboards to get cabin temp correct for the pax before boarding.
regards alan. 8)
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Pistonpilot
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Re: Engines start sequence (3-4-2-1): why?

Post by Pistonpilot »

Some aircraft start sequences are determined by the placement of accessories on the engines, too. Things like manual start valve access on airliners. It's usually safety related, either safety for ground crew or egress for air crew/pax...or both!

-Ian C

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ilya1502
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Re: Engines start sequence (3-4-2-1): why?

Post by ilya1502 »

Thanks, the matter is much clearer now.

One practical concern though. If I start right engines beforehand to warm up the cabin and provide it with electricity, then board passengers, and only then start engines #1 and #2, I have to warm up engines #1 & #2 and this can take quite a while in cold winter weather, like 20 minutes, before I can taxi for takeoff. So how did it work in those piston liners? Passengers just had to patiently wait sitting there (what choice they could have)? Did airline schedules account for these time delays in winter?

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CAPFlyer
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Re: Engines start sequence (3-4-2-1): why?

Post by CAPFlyer »

Real world, the mechanics started and warmed the airplane before the start of every day. They usually also did the in-depth run-up so that the Flight Engineer and crew didn't have to spend as much time at the end of the runway (the crew would simply do the runup with mag check and then check the props and that's it. No feather check, no full prop run, just the making sure they cycle properly).

So, if you're operating in really cold weather with these planes, my suggestion would be to plan to start earlier than you think, run the engines to get them warm, shut down, board your passengers, and then do your flight.
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ilya1502
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Re: Engines start sequence (3-4-2-1): why?

Post by ilya1502 »

Thanks, CAPFlyer. Generally, I presumed a similar procedure.

Tobus75
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Re: Engines start sequence (3-4-2-1): why?

Post by Tobus75 »

ilya1502 wrote:Thanks, the matter is much clearer now.

One practical concern though. If I start right engines beforehand to warm up the cabin and provide it with electricity, then board passengers, and only then start engines #1 and #2, I have to warm up engines #1 & #2 and this can take quite a while in cold winter weather, like 20 minutes, before I can taxi for takeoff. So how did it work in those piston liners? Passengers just had to patiently wait sitting there (what choice they could have)? Did airline schedules account for these time delays in winter?
You can run cold engines fine for taxi, just not full power for take off. By the time taxi is done engines are probably warmed up. If not only a little time left to further warm them up.
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