TAS increases when Weight decreases
Thread Starter
Joined: Oct 2010
Posts: 356
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From: France
TAS increases when Weight decreases
In the Cessna 172S POH, a note to the cruise performance tables says that you may add 1kt per 150LBS below MTOW.
There's no such note in the 182RG POH.
So I was wondering if I could derive that information from the performance tables.
For different RPM/Manifold settings, and altitudes, the table gives the %Power and the TAS.
I could try to write the equations of Lift, Drag, and Power. From the tables I think I could get a sort of Cx as a function of Cz, and then at the end get my answer.
As I don't want to reinvent the wheel, I would like to know:
Is there a simple rule of thumb everybody knows but me?
Do my ideas to solve the problem make any sense at all?
As anyone any link to a well documented solution?
Thank you all for your answers
There's no such note in the 182RG POH.
So I was wondering if I could derive that information from the performance tables.
For different RPM/Manifold settings, and altitudes, the table gives the %Power and the TAS.
I could try to write the equations of Lift, Drag, and Power. From the tables I think I could get a sort of Cx as a function of Cz, and then at the end get my answer.
As I don't want to reinvent the wheel, I would like to know:
Is there a simple rule of thumb everybody knows but me?
Do my ideas to solve the problem make any sense at all?
As anyone any link to a well documented solution?
Thank you all for your answers
Joined: Mar 2005
Posts: 1,338
Likes: 1
From: Uh... Where was I?
Long time I don't fly one of those...
What I remember is that in those airplanes, performance is usually referred to a fixed weight, typically MTOW. They don't bother in giving multiple tables for different weight ranges.
For the same power setting, TAS should increase when weight decreases. According to your 172 POH, this is at the rate of 1 kt per each 150 lb decrease. In the other one there's nothing written, Right? It can be either because they forgot to add the note or because the effect is negligible in that airplane.
Just guessing
What I remember is that in those airplanes, performance is usually referred to a fixed weight, typically MTOW. They don't bother in giving multiple tables for different weight ranges.
For the same power setting, TAS should increase when weight decreases. According to your 172 POH, this is at the rate of 1 kt per each 150 lb decrease. In the other one there's nothing written, Right? It can be either because they forgot to add the note or because the effect is negligible in that airplane.
Just guessing
