A320 Eng Relight Envelope

[pwned]

Hi. Need some help on the engine relight envelope for A320. I'm abit ( actually very) confused. In the QRH there are basically 3 different segments/envelopes.
1- STARTED ASSISTED N2 Less than or equal 18%.
2-STARTED ASSISTED OR QUICK WM RELIGHT. t<30s, N2 >18%.
3-STABILISED WINDMILL.

Can someone explain what that means plz?
Correct me if im wrong plz.

a) IF outside those envelopes, the relight will not be successful ie need to be at FL 300 or below. Correct?

b) If in the Stabilised Windmill envelope, the failed engine does NOT require additional Bleed for the relight. Correct?

c)If in the STARTED ASSISTED N2 less than or equal 18%, means the Start Valve will be OPened by Fadec to allow bleed air to assist in the Relight. Correct? BUT WHat is the N2 18% thing for?

d) I have absolutely no idea STARTED ASSISTED OR QUICK WM RELIGHT t<30s, N2>18% means at all.....if within this envelope, what do i need to do? what is QUICK WM Relight vs STABILISED WM?

Thank you.

[rudderrudderrat]

Hi pwned,

a) = Correct.
b) = Correct.

c & d) FCOM Eng Relight in Flight procedure says:
" X Bleed Valve ... Open
If outside the windmilling start envelope, the FADEC will open the starter valve."

That line takes the "thinking pilot" out of the procedure, because the QRH requests the X Bleed valve to be opened regardless of whether the starter will be used or not. FADEC looks to see if N2 <18%, (which will require a start assist) or N2>18% (will not require a start assist) and hence decides whether to open the starter valve or not.

There are basically 3 areas to the start envelope:
1) N2 definitely >> 18% = Stabilised Windmill. (But the big airflow may blow the "candle" flame out occasionally)
2) N2 definitely < 18% = Starter assist required.
3) N2 probably about 18% = Starter Assist (if N2 <18%) or Quick Windmill area if N2 >18% (and the relight was consistently demonstrated to occur within 30 secs of fuel flow.)

Hence the caution note to time the 30 secs from fuel flow to light up.

[pwned]

Thanks rudderrudderat.
So am i right to say that the idea of the start envelope is only to make sure your Alt/speed is within ANY of the shaded area (since once you in any of the shaded area and regardless of the N2 %, the actions are the same. Turn on the X bleed , turn off the wing a ice, and eng master switch on and let fadec decides whether to open the start valve or not) ?

Thanks once again :)

[Microburst2002]

It is interesting to note that, according to somewhere in the FCTM, the optimum speed for assisted engine relight is green dot.

[Netburn]

"Green dot, which corresponds to the optimum relight speed with starter assist, is displayed on the
left PFD. With starter assist (APU bleed), only one engine must be started at a time."

But that's only for ALL ENGINE FLAMEOUT.

Regards.

[Natstrackalpha]

ding ding ding ding - eng failure - number 2 eng.


Silences horn, confirms, and confirms which one - and which thr leve to close and closes thrust lever - when does re-light occur what causes it from MR. Fadec?


Is it because you select IGN or because you did not sw Eng Master off?


What trigger starts the re-light procedure? Cruising along as we were.


Or is it simply due to the failure where Mr Fadec says, oops no engine, lets give it a go.

[Goldenrivett]

when does re-light occur what causes it from MR. Fadec?

DSC, 70 Power Plant, 80 Ignition & Starting, 30 Ignition system, Continuous ignition - Diagram shows Continuous Ignition is automatically selected If Flame Out Detected.

[Natstrackalpha]

Thank you Goldenrivett.

[sonicbum]

ding ding ding ding - eng failure - number 2 eng.


Silences horn,

One ding only, no need to silence anything then ;-)

[IFLY_INDIGO]

frankly the graph is confusing and useless.. Actions are same no matter where you are inside that graph. IGNORE THE GRAPH

[Citation2]

Well firstly it is of vital importance for your situational awareness.
Secondly you might have dispatched the aircraft by MEL with a start valve inop.
Then if you suffered an engine failure, and attempted a relight in the start assisted envelope , you will not understand why the relight was not successful ( start valve inop)
Conversely , if you knew your envelope you could anticipate and plan forward for a speed that falls into the windmill envelope in order to have a successful relight at first hand , and avoid an unduly unsuccesful start attempt.

[IFLY_INDIGO]

But Actions are same, no matter where you are in the graph

[Scott5]

"FADEC looks to see if N2 <18%, (which will require a start assist) or N2>18% (will not require a start assist) and hence decides whether to open the starter valve or not."

This thread is pretty old but hopefully someone around that can help with this.

Regarding our aeroplanes with IVE engines there is a comment FCOM DSC MANUAL STARTING;

"In flight, the FADEC always commands a starter-assisted start"
This comment is not consistent with FADEC looking at N2 below or above 18% and commanding Start Valve open or not.
Can someone please comment on the significance of this.

In the NEO aeroplanes P&W engines this comment doesn't exist?
Does the same logic apply, FADEC looks at N2?
If so, what is this N2 value? Is it 15% as per the relight envelope?