Boeing Starting Engine No. 2 First?
 

Hi,

I got asked a question from a friend regarding engine start on number 2 first.

Looking at the pneumatic system of a B737 it would be more logical to start the Number 1 engine because the bleed air from the APU is closer to the engine than it is to the right engine.

The isolation valve in open or auto ensures that apu bleed air reaches the no2 starter.

The habit of no2 starting first is simply because it's on the opposite side of the airbridge. When starting with external air and/or power it is usual to start no1 for the same reason (further away from the carts).

starting no 2 engine first........not only Boeing. same technique on Airbus and guess on all "the rest". Reason: see above post.

Starting No2 Engine first.
 

In regard to the B737, the reason the #2 engine is started first is if you look at the Electrical Schematic, you will see from where the TR3 is powered. It is from the R/H AC Bus. The #3 TR is the essential TR from which significant avionics is powered. So, you want to have this TR powered up and running first in the event you lose AC power to the aircraft during start.

Everyone thanks for your input!

Jetz your answer sounds good but if you lose AC power on start your going nowhere except back to the stand plus your on APU power so TR3 would already be powered, right?

As I see everything is pointing to engine 1.
APU bleed is closer to engine one.
The Headset jack is on the RHS allowing engine 1 to be clear on the push.
The GPU and Air cart is on the RHS.

The only thing that is on the LHS is the punters but then again you wouldnt start the engine on stand with people boarding, and the airbridge is well out of the way on push.

May be its just a Boeing thing and Airbus copied :ok:

Alternative views - Starts 2 first coz...

The bleed sides can then be split allowing pack on in hot weather whilst starting the other one.

The APU consumes fuel from the No1 tank, starting 2 first takes a little fuel from the no2 tank balancing things before you go.

Coz its always been done that way.

The first officers ears are less important than mine (who said that - speak up man, I'm deaf!)

On the 737 in all reality, it doesn't make a jot of difference. On the bus it does as the brake system gets topped up before the engine develops any meaningful thrust. I believe some of the bus series start the other one first because the system is the other way round.

Surely partly historical too?

The main passengers doors are on the left hand side. On the B707 we always started 3,4,2,1 - you could be winding up 3 and 4 whilst the last pax were boarding, main pax door being closed and the steps were being taken away.

I imagine those silly Health & Safety Rules prevent us from doing similar these days.

That's what we do in the 717. Start left/1, ISOL>Auto ie closes, then left pack on, then start right/2. Aircon whilst we wait eons for second engine to start is good! :ok:

We don't do that as if an evacuation was required eg engine blowup/fire on start none of the slides are armed. :ouch:

As far as i was taought during training, its a procedure that was used to allow no.2 engine to be started before first class passengers boarded then the no.1 after the door was closed so they wouldn't have to wait long before departure on the aircraft.

Ithought on quads you started 3421because when starting 3 if you had fire or anything fire service can approach from right then 4 for same reason then the other side 2 and 1 so fire guys are always able to get to the engines, and on twins number 2 because if fire or evac on start up then most pax will tend to go for the side they boarded and also clear area for fir trucks on right due to no air bridge

start order on 4 engine
 

I have never seen a 747 of any type routinely started in any order other than 4-3-2-1

SB SFO,

Our classics start 4,1,2,3
our -400's start 1&4 together and then 2&3 together. Which is fairly common among 747 operators.

Dear A330-340

on the 320 bus, engine 2 power yellow hydraulic for parking brake(the handle on the pedestal).

once second engine is started(left engine # 1), the brake valve switches from yellow to green, and provide hydraulic pressure for normal braking.

Besides the obvious system dependency reasons,the start sequence is historical.Dates back from way back pre DC3 days when pilots were still pilots and depended to a much lesser degree to their engine instruments(cause they had so few of them!) and/or any ground crew.
By nature the P1 sat on the left seat.When flying a multi engine airplane it seemed prudent to start the 'further' engine,hear its re assuring purr and then start the 'nearer' engine and again hear the purr before chocks off.
The nearer engine,needless to say would be the left or number 1 engine and vice versa.
If done in reverse order chances were that the right engine sound would be drowned in the sound of the left,therby not completely reassuring our 'fly by the seat of his pants and by the sound of the drone' pilot.
This is what info I have.
Of course one mustn't forget that these were the days when pilots litreally flew by the seat of their pants and were still aviators...
Sounds and sights were of paramount importance. And things never changed thereafter.Systems were developed so as to enable and support a right/left sequence.And a 4,3,2,1 sequence in quads.
Off now...:cool:

...our -400s start 4&3 together and then 2&1 together.

There is nothing in the Boeing 737 book that says which engine should be started first, except of course for one or two of the Supplementary Procedures.

It makes sense to start the engine on the same side as the ground engineer, away from the side of latest activity and which can provide conditioned air the soonest.

As a point of personal interest, I've noticed that that Engine 2 start EGTs are generally higher which I think is due to starting on APU bleed. Starting No. 1 first on hot turnarounds and/or where the aircraft has a bit of a tendency to hot start (nearly always No.1 again) and even a crossbleed start on one aircraft that was going through a time of being particularly prone seem to work well.

The old-lady (B707) sequence was 3-4-2-1!

Flaperon777....great explanation....!!! :ok::ok:
I faintly remember my ol man(an old bold pilot of yesteryears)mention something similar eons ago.And now I hear you say it again...:).
Couldnt have summarised it better myself!

Let me guess!

GE

RR
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And as far as i know most -400 operators with PWs start one at a time.
such as: 4-1-3-2