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1 vote
2 answers
365 views

For a fixed density altitude, how does climb performance depend on pressure altitude?

Below is the climb performance from the 1978 Cessna 152 POH, which I've plotted as climb rate versus density altitude. It shows that higher pressure altitude gives decreased performance even when the ...
Chris's user avatar
  • 18.2k
0 votes
1 answer
254 views

How to calculate boundary layer thickness?

So I have a flat plate with a surface of 7sqm and an aspect ratio of 12 with air blowing straight at it (like a wing) at a speed of 50km/h. I would like to manually calculate the thickness of the ...
Vincent Cerowski's user avatar
9 votes
2 answers
1k views

Why do helicopter performance charts for hover out of ground effect (HOGE) have a "knee"?

Have a look at the following performance charts from Section 5 of Robinson R-22 Pilots Operating Handbook for hover out of ground effect (HOGE). If the temperature and gross weight are known, the ...
Igor's user avatar
  • 107
0 votes
2 answers
402 views

I don't quite understand the derivative in this vertical wind gust formula

First my english writing skill is still bad so pardon me if i accidentally made any mistake TT-TT. So recently I have learnt about how the vertical gust affect the load factor and the calculation ...
Harry Huynh's user avatar
3 votes
1 answer
664 views

What methods are used for calculating maximum takeoff windspeed of a helicopter?

I would like to calculate the maximum windspeed in which a helicopter may safely take off and safely land, assuming a theoretical wind environment with constant wind direction and no gusts. I ...
max's user avatar
  • 131
1 vote
1 answer
2k views

How do you calculate Profile Drag?

second year aeronautical engineering student here. I'm doing some aerodynamics coursework but have run into a problem. I've read through the answers to the question "what is profile drag?" but ...
Forgot my Username's user avatar
5 votes
9 answers
16k views

How does maximum speed vary with altitude?

Question: How does a commercial jetliner's highest possible groundspeed vary with altitude (assuming wind=0) ? My understanding is that drag decreases with altitude, therefore maxspeed increases with ...
summerrain's user avatar
  • 3,656
1 vote
2 answers
3k views

How to calculate the induced drag coefficient?

In an exercice of Flight mechanic, I have to compute the drag coefficient at zero lift: $C_{D0}$.We saw in class two ways to find it : $$ C_{D0} = \frac{\pi AR e}{4E_{max}^2} $$ With $AR$ the aspect ...
Louis Etienne's user avatar
1 vote
3 answers
2k views

Propeller Characteristics at Different Altitudes

Assuming I have a propeller with a given diameter (D), pitch, blade twist, and number of blades, I can theoretically analyze discrete airfoil sections in XFOIL and come up with lift and drag polars ...
dumbpropnerd's user avatar
3 votes
2 answers
5k views

How to realistically model propeller static thrust?

I am graphing static thrust vs prop diameter for a 600 kW motor and a prop diameter up to 5 m. I have seen the post 'What is the equation for calculating static thrust?' and using its formula and ...
Pilothead's user avatar
  • 21k
4 votes
1 answer
438 views

Is it possible to determine a rotation speed (Vr) using other known V-Speeds?

Is it possible to come up with a good estimate of rotation speed using other known V-Speeds? For example: if I know a plane has a Vs @ 55kt. and a ...
Ryan Griffith's user avatar
6 votes
1 answer
13k views

How is the zero-lift drag coefficient calculated?

The drag coefficient is usually given as a funtion of the lift coefficient and the zero-lift drag coefficient ($c_{D0}$): $c_D=c_{D0}+k\cdot c_L^2$ How can I calculate/estimate $c_{D0}$?
Robe's user avatar
  • 617
7 votes
1 answer
521 views

For jets, how can we show that 1/2*ρ*V^2 is equivalent to 1481.3*δ*M^2?

In Roskam's book, we find the following relationship given for climb performance in jet aircraft: Thrust requested = $D$ = $C_d \cdot (1/2 \cdot \rho \cdot V^2) \cdot S = C_d \cdot (1481.3 \cdot \...
d.pensopositivo's user avatar