Boeing Starting Engine No. 2 First?

[punk666]

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.

[shlittlenellie]

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).

[Airbus_a321]

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

[JETZ Tech]

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.

[A330-343E]

Another reason to start No.2 engine on the Airbus (e.g. A320) is that the right engine drives the hydraulic system on the brakes. Correct me if this is incorrect.

[punk666]

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:

[Cough]

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.

[fireflybob]

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.

[Capn Bloggs]

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

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

[767200ER]

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.

[AI101]

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

[sb_sfo]

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

[Willit Run]

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.

[flyhelico]

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.

[Flaperon777]

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:

[L337]

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.

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

[Sciolistes]

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.

[169west]

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

[King on a Wing]

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!

[B-HKD]

Let me guess!

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

GE

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

RR
---------------------

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

[spannersatKL]

Most operators of 747s I have worked with its 4 1 2 3....
4 for Brakes (Also Electrical Power, ESS Bus from this side)
1 for Steering/Brakes, Also powers other side of sync bus.
2 (Brakes again!!) Proper Redundancy there eh!
Then 3

[Pugilistic Animus]

For those whose APU has enough power to start both,...is it ever done?

I picture most ops manuals being touchy about that

[Willit Run]

On the -400, dual starts is very common.

since I have not operated anything else than G.E.'s on the -400, I cannot say about other engine types and their stating sequence.

[Swedish Steve]

For those whose APU has enough power to start both,...is it ever done?

The MH B777 that I used to look after at ARN normally started both engines together. Whole process took about 30 secs from Clear to start, to Clear to disconnect.

[A and C]

Flaperon777 Has most of the historic answers but a little thin on historic technical detail.

Historicly the #2 engine had the generator and the #1 had the hydrulic pump so the battery was mounted nearest to the #2 engine to enable the shortest cable run to reduce the electrical losses due to resistance.

So the #2 was the best engine to start in order to save the small amount of electrical power that these aircraft had in the batterys and once it was running to have a generator on line to help start the #1 engine.

The Beech King Air has the battery mounted in the wing just inboard of the engine, in these modern times I suspect Beech mounted the battery in this location because thats the way they had done it in the past.

[Rick777]

With the exception of the B707 which we started in the order previously stated, most of my experience with both Boeing and Airbus was to start 1 first. I guess each operator has their own reasons. Boeing training-at least on the 777 does not have a preference for 1 or 2.

[flyboyike]

I wonder what the sequence is on the B-52. Or the An-225, for that matter.

[yotty]

737-3/4/5 engine start 2 first due to the fact that if the isolation valve fails you find out before you waste an engine start. Isolation valve failure is a no-go item.:ok:

[NSEU]

On our RR's and GE's (747-400), we start 4, 3 then 1&2.

I really don't think you can claim that procedures are truly "common" until you have worked for every airline :ok:

[celtic mech]

As flyhelico (http://www.pprune.org/members/323946-flyhelico)
"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."

This is correct. Also on the A330, engine # 1 started first as the 2 Hydraulic Pumps on it (Blue and green Systems) will allow normal braking and Alternate braking upon start up immediately.

[Bolty McBolt]

Boeing start No. 2 first

I asked same question many years ago, why #2 engine (#4 on the 747, 744 ) started first.

I was told at the time, it was for 2 reasons.
1, As previously discussed this engine drives the hydraulic pump that supplies the primary braking source,
2, The "essential" power BUS normal source also comes from this engines'
generator. ( Not quite true in the 767)

When you look at the A330 the Primary and Alternate green and blue hydraulic brake source come from Engine 1, as well as the normal Essential power supply is also from Engine 1.

Does the A330 start engine 1 first??

[zonnair]

Jep. 330 start first ENG 1.

[SixPin]

The main reason is HISTORIC.:ok:
“Back in the day” on the old piston props the crew would start No 2 while the Px were boarding on the left side door.
On turn around they would shut-down 1 to disembark and board the next load and keep 2 running. What’s more, the only reason 1 was shut down, was because it was too noisy for the Px, nothing to do with safety.
Ahhh! Those were the days!
:)
How do I know? My dad used to fly them.
;)

[Mr.Vortex]

IMHO, right engine was choose because

- it was connect to cabin air condition pack and help passengers from getting sweat. [For ex. B737]
- Hydraulic pressure for brake.
- may be reduce the risk for ground staff since the cargo loading and gate are
done on the left side.

Best regards

[aveng]

The starting order always corresponds to the engine hydraulic pump that supplies the brake system.
A330 #1 = green + blue hyd pumps = normal + alternate/parking braking.
737 #2 = B sys hyd pump = normal braking.
767 #2 = R hyd system = normal braking.
744 #4 = #4 hyd system = normal braking.

[aviatorhi]

If you're pushing back you can't really justify starting #1 or #2 first based on which one is farther from the jetway, but here's an important thing to think about...

Boeing used to power A hydraulics with EDPs (Engine Driven Pumps) and B hyrdaulics with EMDPs (Electric Motor Drive Pumps, also, I realize some aircraft have more systems in general and there are also AUX and STBY systems on others, but let's stick to the basic 2 system layout). This was fine until they came up with the crazy idea of only slinging 2 engines under a plane. The first 737s (100 and 200) did have this same layout of pumps, but starting with the 300 Boeing began putting one of each on each system, for greater redundency.

What does this mean to you?

Well if we look in our Boeing books you'll notice that A hydraulics power nosewheel steering and B powers brakes (among other things). Being under tow/push you have no use or A system (in fact it can be quite dangerous given the circumstances on the ground to pressurize the A system up during push). You also have a lot of use for B system, namely, the Brakes. This is part of the reason starting with #2 is a good idea. But, there is one more, turning the A pumps off during push is part of many checklists, but having them selected off and actually being off are two different things, you see. EDPs on many Boeing are "powered off", which means if that if you were to lose power during pushback with an engine which powers an EDP running (#1 on 733 and later) you would pressurize that system, with potentially dangerous/deadly results. Losing power with #2 running wouldn't do a thing other than keep B system pressurized when the EMDP goes offline due to the same power (AC) loss.

[A37575]

A certain amount of tradition may come into the starting order which was 3,4,2,1. On Lancasters (and the Lincolns I flew) The starboard inner (No 3 engine) was started first because the compressor for charging the air bottle to 450 PSI was installed on that engine. That gave air to the wheel brakes, electro-pneumatic rams for the radiator shutters on the Rolls Royce Merlin engines, slow running cut-out controls, automatic supercharger change and air cleaners. A generator was also installed on both inboard engines.

The port inner had one hydraulic pump that operated the bomb doors, flaps, fuel jettisoning and undercarriage. In addition a compressor on the No. 2 engine operated the autopilot.