PMC
Thread Starter
Joined: Jan 2007
Posts: 30
Likes: 0
From: italy
PMC
Condition..... RWY condaminated, PMC inop. On short RWY we are limited by V1mcg so...the V1 is the V1mcg but in this situation our V1mcg is increased by 4 kts. this means that I'll go to do my RTO faster....how can I corresct for this my calculation?
Joined: Feb 2005
Posts: 4,581
Likes: 0
From: flyover country USA
If it's a 737 classic (CFM56-3) PMC = Power Management Control (analogue N1 control).
PMC inop means no control loop on N1, thus less precise control and aggravated worst-case assymetrical thrust.
PMC inop means no control loop on N1, thus less precise control and aggravated worst-case assymetrical thrust.
Moderator
Joined: Apr 2004
Posts: 794
Likes: 0
From: Rome
Suppose you V1mcg is 116 kts. You add 4 kts due to PMC OFF, and you get 120 kts. Then you have to subtract a certain amount of knots to your actual V1 due to the SSW condition. You will be anyway limited by your actual V1mcg.
(me thinks)
(me thinks)
Joined: Sep 2005
Posts: 30
Likes: 0
From: bah...
I-2021, the new V1 will be 120 anyway.
Not less than that.
So the question is about aborting at too high a speed to stop in time.
But since the N1 will be higher than normal (increasing with airspeed), the higher V1 will be reached at about the same distance from brake release (faster acceleration).
Ciao ragazzi!
Not less than that.
So the question is about aborting at too high a speed to stop in time.
But since the N1 will be higher than normal (increasing with airspeed), the higher V1 will be reached at about the same distance from brake release (faster acceleration).
Ciao ragazzi!
FAO ItPilot 737
Joined: Jan 2007
Posts: 43
Likes: 0
From: buderim australia
1.In aus you first calculate your Limit weight and normal Vspeeds from a table or generalised takeoff data.
2. There is a weight decrement to be taken off the field length limit or whatever limit was most limiting on your performance ( climb, V1 mcg, obstacle) in your case it seems the V1 was it.
3.In checking all these you then have a PMC off performance limit weight which with the deecrements applied gives you a buffer in the same way that a derated thrust calculation should give you a buffer ( we use 6 degrees which equates to about 300 metres normal ops. )
4. Practically you understand that the PMC assists the MEC to adjust fuel flow to maintain commanded n1 however as both Pmcs are turned off you will get a slight overboost in thrust as you take off and accelerate down the runway. The overboost combined with the weight based margins make the higher V1 RTO valid without need for further adustment.
Ps I cannot find a limit for PMC off takeoffs on contaminated RW in our OPS but I am not at work.
I think there will be a difference in min V1 because the uk has an allowance for an unfavorable 5 knot xwind and we dont.
You should then find as increase in min v1 ( ours is 2 knots)
2. There is a weight decrement to be taken off the field length limit or whatever limit was most limiting on your performance ( climb, V1 mcg, obstacle) in your case it seems the V1 was it.
3.In checking all these you then have a PMC off performance limit weight which with the deecrements applied gives you a buffer in the same way that a derated thrust calculation should give you a buffer ( we use 6 degrees which equates to about 300 metres normal ops. )
4. Practically you understand that the PMC assists the MEC to adjust fuel flow to maintain commanded n1 however as both Pmcs are turned off you will get a slight overboost in thrust as you take off and accelerate down the runway. The overboost combined with the weight based margins make the higher V1 RTO valid without need for further adustment.
Ps I cannot find a limit for PMC off takeoffs on contaminated RW in our OPS but I am not at work.
I think there will be a difference in min V1 because the uk has an allowance for an unfavorable 5 knot xwind and we dont.
You should then find as increase in min v1 ( ours is 2 knots)
