Take Off N1 Thrust question

[Ray Proudfoot]

I have a question regarding setting take-off thrust. I fly the PMDG737 model but without its panel of course and I have an Aerosoft 747MCP for autopilot control. My throttle is the CH Pro Throttle.

If I set TO1 or TO2 in the CDU the maximum N1 setting will be reflected on the EICAS. But, when I then press THR on the MCP and push the throttles all the way forward N1 exceeds that set on the EICAS. It slowly returns to the N1 value but it doesn't seem right that it should exceed that value in the first place. Things seem better if I don't push the throttles all the way forward.

Is the problem related to the Aerosoft MCP (it's more closely related to the 747 - not a 737) or down to some misunderstanding on my part as to how to engage Take Off thrust?

Guidance would be appreciated by this armchair pilot.

[Bob Reed]

The way I use takeoff power is, and this may not be right, arm auto throttle, advance throttles slowly until 80%n1 is stable then engage TOGA.

[Ray Proudfoot]

The way I use takeoff power is, and this may not be right, arm auto throttle, advance throttles slowly until 80%n1 is stable then engage TOGA.

Thanks Bob. It seems I should help the autothrottle by manually applying the approximate amount of power. The problem is the green indicator on the N1 EICAS doesn't accurately reflect the power setting and often it needs retarding.

Out of interest do you keep the parking brake set until the throttles have been advanced to the approximate N1 value? I don't and I've often wondered what is the correct procedure.

[Bob Reed]

Thanks Bob. It seems I should help the autothrottle by manually applying the approximate amount of power. The problem is the green indicator on the N1 EICAS doesn't accurately reflect the power setting and often it needs retarding.

Out of interest do you keep the parking brake set until the throttles have been advanced to the approximate N1 value? I don't and I've often wondered what is the correct procedure.

Well the parking brake depends on the length of the runway I am on. If it is long and I have room I do not hold the brake but if it is a shorter runway, and I guess this, I hold the brakes until just before 80%N1 and then engage TOGA. Would like to hear from a real pilot on this.

[Trevor Hale]

I know for a fact on smaller runways, The operators of the Falcon 900 Hold the peddles until engines are at T.O. power. then let em go... But Not the parking Brake!

[Ray Proudfoot]

Well the parking brake depends on the length of the runway I am on. If it is long and I have room I do not hold the brake but if it is a shorter runway, and I guess this, I hold the brakes until just before 80%N1 and then engage TOGA. Would like to hear from a real pilot on this.

That sounds pretty sensible. I too would like to know r/w procedures on this. I can almost see Pete D flicking through his 737 procedural manual now. My Mike Ray 737 manual suggests the p/b should be set but in my mind it puts an undue strain on the brakes.

[Bob Reed]

I know for a fact on smaller runways, The operators of the Falcon 900 Hold the peddles until engines are at T.O. power. then let em go... But Not the parking Brake!

I have used both but I did think that the parking brake was probably not the way to do it... But sometimes easer.....

[Peter Dowson]

That sounds pretty sensible. I too would like to know r/w procedures on this. I can almost see Pete D flicking through his 737 procedural manual now. My Mike Ray 737 manual suggests the p/b should be set but in my mind it puts an undue strain on the brakes.

The parking brake is merely a physical lock on the brake pressure in any case, so whether you use foot pressure or the parking brake lever is rather irrelevant. If you have your pmSystems programmed correctly you'd find you have to depress the toe brakes to create the brake pressure then pull the PB handle to lock the pressure on. In that sense it is rather similar to the way the parking brakes operate in a humble Cessna.

Regards

Pete

[Bob Reed]

The parking brake is merely a physical lock on the brake pressure in any case, so whether you use foot pressure or the parking brake lever is rather irrelevant. If you have your pmSystems programmed correctly you'd find you have to depress the toe brakes to create the brake pressure then pull the PB handle to lock the pressure on. In that sense it is rather similar to the way the parking brakes operate in a humble Cessna.

Regards

Pete

Is it possible to program this even with using the Parking Brake release when toe brakes are applied? I have not done too much with PMSystems yet.. Just looking at starting.

[themis]

Real Life Pilots usually set the A/T On when are aligned with the main runway to prevent accidentally press of TOGA button.
Also N1 80% for engine stabilization is way to high...!


The proper way for the 737NG is....(copying from Boeing's FCTM)


"Advance the throttle levers to just above idle (40% N1) as the airplane rolls onto the runway at a slow taxi speed. Once the airplane is aligned with the runway, allow the engines to stabilize momentarily then promptly advance the thrust levers to takeoff thrust (autothrottle TO/GA). Allowing the engines to stabilize provides uniform engine acceleration to takeoff thrust and minimizes directional control problems. This is particularly important if crosswinds exist or the runway surface is slippery. The exact initial setting is not as important as setting symmetrical thrus.

Note: Allowing the engines to stabilize for more than approximately 2 seconds prior to advancing thrust levers to takeoff thrust may adversely affect takeoff distance."

Also,

"A momentarily autothrottle overshoot of 4% N1 may occur but thrust should stabilize at +/- 2% N1 after THR HOLD. Thrust should be adjusted if required by PNF to -0% +1% target N1."


Regards
Themis Katakalos