PDA

View Full Version : 737NG Engine IN-Flight Start Envelope.


B737NG_Pilot
8th Mar 2014, 13:51
Hello Everyone,

Can some one refresh, the significance of 281 knots, in the IN-FLIGHT engine start envelope.

BOAC
8th Mar 2014, 14:15
Where do you find that? Please post an image of the page and specify the a/c type.

RAT 5
8th Mar 2014, 16:56
I assume you are talking about the windmill start envelope. I suspect this is not the NG family as -800 has a different speed. 281kts seems very picky: why not 280; it's easier to remember. Why make an easy job difficult under stress? Anyway the need for speed is to keep the engine turning fast enough to have sufficient air flow to 'jump start' the motor. Slower speed would require a hand crank.

JT8D-17
8th Mar 2014, 19:32
281kts is 100% correct. I never saw it until I looked today. It used to be 275kts before.

de facto
8th Mar 2014, 19:36
On your inflight start enveloppe ,from Fl240 to FL150 the speed of 281 kts is the minimum to be in the windmill area.
Below FL 150 you need a minimum of 300 kts to be within the in flight start enveloppe for windmilling.

The 281 kts is written on the chart and it is for the NG.
Maybe that speed represents the speed at which a successfull relight was demonstrated,again it says successfull starts may be obtained outside of the enveloppe but not assured :p like any other would be...

B737NG_Pilot
9th Mar 2014, 06:31
Thanks defacto and everyone else.:D

Denti
9th Mar 2014, 06:51
Interesting, the envelope in my QRH shows 281kts at a pressure altitude of 24.000ft, but rising in a linear fashion to 300kts at 15.000ft.

I remember that the envelope changed in 2011 once we got the -7BE variant on the line, it used to be somewhat different before that.

de facto
9th Mar 2014, 11:35
The 787 RR need only 250 kts to be in the windmilling area...

RAT 5
9th Mar 2014, 20:54
There are pilots I teach/check who can not fly +/- 5kts on approach, so heaven help them trying to fly 281 kts with a double engine failure. Give it +/- 20kts and they have a chance. Get real guys.

de facto
10th Mar 2014, 12:00
RAT5,

Its not about being able to do it or not.:rolleyes: by the way with loss of both engines,captain should become PF and if your airline captains cant pitch for an airspeed within 10 kts then god have their soul and good for you as you have more teaching to do.
Please go and tell boeing to get real then and change the info (speeds) on their published inflight start enveloppe.