smartt1982
Topic Author
Posts: 226
Joined: Sat Nov 24, 2007 11:17 pm

737 NG Speedbrakes With Min Speed + Min Maneuver

Sun Mar 25, 2012 1:50 pm

Hello,

I know this is probably and more than likely asking a question in regards to basic aviation stuff that I should know but all the same, any information would be very helpful.

I have been recently reading up on the minimum speed (black +Red band) and the minimum manevuer speed (amber band) on the speed tape of the 737 NG in particular the 800 in case there is a difference on the other NGs, but I do not believe there is.

From reading it, my understanding is that the minimum manevuer speed (amber band) gives you a .3G margin in 1G straight and level flight and this will decrease with altitude to adequate etc but it is NOT vary with G-load.
In regards to the minimum speed (black +Red band) it says that it DOES react to an increase in G/wing loading, so if I increase the G for example in a steep turn it will start to increase or get bigger on the speed tape.

One of the things I am confused with this is that both will reflect the effect of extending the flight spoilers.
I am not trying to say that is wrong but I thought the spoilers would only increase the wing loading so hence only the minimum speed (black +Red band) would be affected. How do the flight spoilers effect the minimum manevuer speed (amber band) if is not affected by G/wing loading (apparently!), see next paragraph...

In relation to a more rear C of G, this should decrease minimum manevuer speed (amber band) which to me would suggest that the meneveur speed IS AFFECTED by wing loading. Because with a more forward C of G, the tailplane has to produce more downforce hence the main wings have to produce more lift at a particular AoA so hence more wing loading which increases the minimum manevuer speed (amber band)
Any help or info would be greatly appreciated.

Kind Regards
Stephen

[Edited 2012-03-25 07:37:02]
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: 737 NG Speedbrakes With Min Speed + Min Maneuver

Sun Mar 25, 2012 5:10 pm

Quoting smartt1982 (Thread starter):
I am not trying to say that is wrong but I thought the spoilers would only increase the wing loading so hence only the minimum speed (black +Red band) would be affected. How do the flight spoilers effect the minimum manevuer speed (amber band) if is not affected by G/wing loading (apparently!), see next paragraph...

Spoilers alter the stall AoA of the wing. So, at equal weight, your stall speed moves so your 0.3g margin to stall also moves.

Quoting smartt1982 (Thread starter):
In relation to a more rear C of G, this should decrease minimum manevuer speed (amber band) which to me would suggest that the meneveur speed IS AFFECTED by wing loading. Because with a more forward C of G, the tailplane has to produce more downforce hence the main wings have to produce more lift at a particular AoA so hence more wing loading which increases the minimum manevuer speed (amber band)

I think this is a lost-in-the-noise issue...to the wing, CG shifts look like a change in aircraft weight due to the changing trim force on the tail. The size of the tail forces compared to the weight of the aircraft means that the change in wing loading works out to a change in stall speeds of something like 1 knot or less.

Tom.

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