What Is The Max Tail Wind Limit For CFM 56-5B at Start Up ?

[kuwait340]

Hello....

i fly the A320 powered by CFM 56-5B high bypass ration turbo fan engines.

any idea what is the max tail wind it can take during engine start ?

thanks

[Capt Claret]

The BR715 as fitted to the Douglas Boeing 717 requires reversers to be deployed if starting with a tailwind component in excess of 25kt.

Doesn't the Bus FCOM give the limit?

[EMB170]

I had the same question about my aircraft type and the manufacturer said if it is not in the manual there is no limit, got to add that was aircraft and not engine manufacturer, it's a Rolls Royce engine.

[BelArgUSA]

Starting with tailwind on hi-bypass engines...

Hola Kuwait340 -
xxx
Sorry, I dont have anything specific about the CFM-56, and no experience in the A-320... I flew the DC8-70s with 4 CFM-56s long ago in the "last century", do not recall of a specific limit of tailwinds, but yes - I recall that we were supposed to be more careful starting with tailwinds than with the "regular" engines... There were no limitations in the AFM...
xxx
I can however pass along some recommendations which I apply presently with the engines I operate, the JT9D-7Qs for the 747-200s. You can probably "translate" the recommendations and "convert" the info to some applicable numbers for your CFMs...
xxx
Yes, in the classroom or the briefings, we insist on avoiding strong tailwinds for start, but in some cases, it is not avoidable -
xxx
Try to "motor" the engine at the highest possible N2, but with more concern for the N1 you need to have - Normally, we need at least 20% N2 to move the fuel "ON", but if N2 is INOP, our N1 minimum is 4%... With a tailwind we insist on having N1 at a minimum of 5%, and I am more concerned of N1 minimum than N2... Keep a sharp eye on EGT rise (potential of hot starts) and monitor the N1 spooling-up to be normal (again, less concern with N2).
xxx
Fact is - do not combine potential problems (APU with unsufficient airbleed start pressure with tailwinds) or ground airstart units which lack "vitamins" with a strong tailwind. Consider also amending which engine you start first, in case your airline SOP is to start the nş 2 engine first, with a tailwind coming from 4 or 5 o´clock relative to the airplane, I would start the engine closer to the fuselage, on the opposite side, possibly, the tailwind there will be reduced.
xxx
This are the only recommendations I can give you -

Happy contrails

[kuwait340]

hello...

our FCOM doesn't mention any limitation on the max tailwind to start the engine.

BelArgUSA
thank you very much for your great explanation...you are always a great help.

thanx guys

[Dani]

Airbus and most probably also Boeing don't give a value for tail wind for its CFM fitted aircraft.

The reason is simply that it depends not only on the wind, but also on other parameters, I can imagine the state of the engine, the temperatures aso.

So AI recommends to do a manual start whenever you have tailwind, knowing that most of the time people wont do it
But they are covered if something happens. CFM and IAE engines have proven to be very stable even with strong tailwind conditions during startup.

hth,
Dani

[kuwait340]

Hello Dani...

in my opinion the Auto start or Manual start are not very different on the airbus A320 fitted with the CFM 56...because :

in the Auto start the LP fuel valve will open at 22% N2 (Very close to the Max motoring Value)

and in the Manual start the recommendation is to set the LP fuel valve (engine master switch) when the N2 Reaches more than 20% or reaches the Max motoring value.

and i have noticed the max motoring value is almost 24-25% N2.

Good Day.

[Kiwiguy]

Shoot at Wellington they pushback into 80 knot winds and still do engine starts.

[Dream Land]

Kuwait, never had a problem starting due to tail winds over a ten year period, the book will give you the conditions when Manual start should be considered, this is one of them.