PDA

View Full Version : startup EGT, wshr g/a & window ovht queries


concordski
26th Feb 2008, 01:19
1) Have heard and curious...if you delay opening the engine start levers (Boeing) until after the recommended 25% (say, to 30%) you can make the peak EGT on startup lower and ease engine life. Why is this?

2) Wshr go-around. Hitting toga once gives toga thrust with the appropriate de-rate as calculated by the EECs, but a second push will give you full toga - you can then disconnect and firewall as required. Is this right?

3) Window ovht u/s - QRH says limit speed to 250 blw FL100. Why does this only apply below? Something to do with a warmer temperature?

The books not very helpful on these three at all...

mustangsally
26th Feb 2008, 01:45
1. Do it at the recommended RMP produces a smoother RPM increace. Applying fuel and spark at higher RMP may reduce the peak temperature but may introduce a less even RPM increase. Don't you think that the engine manufacture would have suggested or recommended a higher RPM if it was better?

2. Our company does not recommend the use to TOGO, we advance the thrust levers manually for all missed approaches.

3. Window heat, simple....."bird strike protection." Without window heat the cold with heat much stronger.

barit1
26th Feb 2008, 01:50
I recall an alternate start procedure with delayed "fuel on" - used for low starter air pressure, tailwind, other adverse conditions - under normal circumstances the EGT reduction was small, but it might make a bigger difference when cards are stacked against you.

Stick'n'Rudder
26th Feb 2008, 12:07
2) Wshr go-around. Hitting toga once gives toga thrust with the appropriate de-rate as calculated by the EECs, but a second push will give you full toga - you can then disconnect and firewall as required. Is this right?Correct about the thrust sequence commanded by the autothrottle.

When encountering a windshear, I'd opt to press the TO/GA buttons at least once to make sure the Flight Director appears (if off previously) and command steady track and GA pitch. Afterwards, I'd just force the trust levers forward, overriding the commands of the autothrottle while disengaging the same to keep the levers full forward.

UL975
26th Feb 2008, 17:08
Not sure what a/c you are on. In reference to the w/shear GA…..
Does one push of the TOGA button give you derated thrust or does it give you thrust to maintain a set (eg 2000ft/min B777) rate of climb? Which may or may not be Full GA thrust.

Stick'n'Rudder
27th Feb 2008, 09:21
Does one push of the TOGA button give you derated thrust or does it give you thrust to maintain a set (eg 2000ft/min B777) rate of climb? Which may or may not be Full GA thrust.

According to my 737-300/500 operations manual, one push of the TO/GA button commands the autothrottle to maintain a "1,000 to 2,000 ft per minute climb rate". It does not give details on what parameters are used to decide which end of the range it will aim for. Ballpark figure for the engines should be around 80 % N1 in normal G/A conditions (i.e. no windshear).

This is accompanied by an initial pitch attitude until passing a certain vertical speed, then will transition to a pitch being function of flap setting and commanded speed, which in turn is again depending on the flap position.

Stick'n'Rudder
27th Feb 2008, 09:25
2. Our company does not recommend the use to TOGO, we advance the thrust levers manually for all missed approaches.

Could you outline which procedures regarding flight director and/or autopilot input you would use? Especially interesting is the part how you get out of the APP mode...

(/me assuming you fly the 737 :hmm:)