Author Topic: I really wish Pyro would chime in soon (Read 1361 times)

Naudet · « **Reply #60 on:** June 26, 2002, 05:49:59 AM »

@Henning: I know that calculations, as i own a hardcopy of that report (about 10 pages).

But as i have no clue of any flight performance calculations, i don't have any idea what those terms and facts mean.

can you explain me what the following are and what they mean?

Ca

Cwg*F

∆fs

Cwg/Ca

Va (i guess that is speed, and as all other speeds are given in TAS and have the index "w" i guess "a" stands for IAS)

and the last term i can really identify, looks like

Ns* did not work, but it said: Wurzel aus gamma durch gamma 0

would really help if i got a definition for em.

If possible in german so i get it all.

HoHun · « **Reply #61 on:** June 26, 2002, 08:36:41 AM »

Hi Naudet,

Ca: Auftriebsbeiwert = Cl: lift coeffecient

Cwg*F: Widerstandsbeiwert * Stirnfläche = Cd * A: Drag coefficient * frontal area

Delta Fs: Zusätzliche Stirnfläche bei erhöhten Anstellwinkel = additional frontal area at increased angle of attack

Cwg/Ca: Verhältnis von Widerstand zu Auftrieb = Cd/Cl drag to lift ratio

Va: Angezeigte Fahrt = indicated airspeed

Vw: Wahre Fahrt = true air speed

>and the last term i can really identify

That's power corrected for air density so that it applies to sea level.

Regards,

Henning (HoHun)

Naudet · « **Reply #62 on:** June 26, 2002, 02:44:25 PM »

Thanks alot.

Does that now mean that damned D9 flew at a mighty 611 km/h (~380 mph) with 1925PS at SL?

Cause i see no altitude given in the calculations.

HoHun · « **Reply #63 on:** June 26, 2002, 03:57:48 PM »

Hi Naudet,

>Does that now mean that damned D9 flew at a mighty 611 km/h (~380 mph) with 1925PS at SL?

Yes.

>Cause i see no altitude given in the calculations.

The calculations describe an equilibrium between weight and lift ("Schwebeflug") independend of altitude. You can see that as "Va" is stated, not "Vw". To find out the top speed of the D-9 for any altitude and any power, you just plug in the actual power value, select the corresponding line in the table, find the indicated air speed and transform it to true air speed. If you plug in 1925 PS @ 0 km, IAS equals TAS, so you get 611 km/h TAS.

Regards,

Henning (HoHun)

Naudet · « **Reply #64 on:** June 26, 2002, 05:29:23 PM »

OK, just to get it right:

Lets say i know the D9 engine would give 653 PS @ 7,5 km (to all folks, thats JUST an example), to get the speed, it would look along the 653 PS line, take the 402 km/h IAS, convert it to TAS and would have the max possible speed for the D9 with 653PS at 7,5 km?

right?

HoHun · « **Reply #65 on:** June 26, 2002, 06:46:17 PM »

Hi Naudet,

>right?

At least that's the way I understood that data sheet :-)

It does not contain complete calculations, though, but just certain data points that were considered important for future reference, so it's hard to decode.

Regards,

Henning (HoHun)

Naudet · « **Reply #66 on:** June 27, 2002, 04:11:29 AM »

Yes, as far as i understand this report, its presents just the results.

And only very important "corner" data is given.

Would be really cool to have the whole calculation step by step.