Hawk 75 and Dewo airspeeds

[rgold]

If you look at the info in game for the unit it says the hawk 75s top speed is 515 and the Dewos is 540. yet while flying level max/max neither will get anywhere near 500

Dewo was at a steady 430 while hawk was around 410..is the plane gauge wrong or speeds for plane off?

[eigenman]

What altitude did you test at?

[kamel]

You need to distinguish between True Air speed and Indicated Air Speed.

Air pressure differences with altitude will result in your indicated air speed [what your instruments show] being different from your true air speed.

Google it.

[rgold]

I noticed it flying just under 2k going from Ant to Dord the other day, not like i was at 9k with gauge showing 180

[eigenman]

WEP on or off?

[rgold]

weapon was off. tried with weapon on but only got over 500 if i included a dive in some way

[petie]

fyi WEP means War emergency power

Not weapon

[eigenman]

Well I tried the Dewo at sea level max/max WEP on and trimmed it out to level flight. The best I could do was about 500KPH. Have not really flown the Dewo much so not sure if I've got it exactly right in setup. Someone else give this a shot.

[Redwing]

Hawk 75 has a hard time going over 440 level flight with WEP on. Was wondering why it felt so dang slow

[Tigger6]

Well I tried the Dewo at sea level max/max WEP on and trimmed it out to level flight. The best I could do was about 500KPH. Have not really flown the Dewo much so not sure if I've got it exactly right in setup. Someone else give this a shot.

I suppose you calculated the TAS as distance traveled/time instead of using the IAS? (Also, this seems too much. Pulling from memory, the e4 should do about 503 km/h or so, so the Dewo should do less than 500)

Edited May 15, 2012 by Tigger6

[eigenman]

I suppose you calculated the TAS as distance traveled/time instead of using the IAS? (Also' date=' this seems too much. Pulling from memory, the e4 should do about 503 km/h or so, so the Dewo should do less than 500)[/quote']

No I was just using IAS at sea level which should be as close to TAS as needed since there is no wind and temperature is a constant 10 degrees C. I'm not sure the distances are scaled correctly enough in the game to actually measure a ground speed.

I guess I should just test all planes and see if they are all that off at sea level. If so then there is a parameter I'm missing.

[eigenman]

Also I ever quite got 500 with the Dewo so it was prolly around 490-495. I also don't know if max speed is achieved with empty fuel tanks because I didn't want to fly around for 3 hours.

[DOC]

1. Airspeed at sea level is the only altitude where IAS (indicated air speed, being that displayed on the gauge) is virtually the same as TAS (true air speed, being your actual speed across the ground) ... as altitude increases above sea level the decrease in air pressure causes IAS to reduce (as the air pressure forced down the pitot tube that drives the speedometer gauge decreases with altitude) while your TAS (the real speed you are going across the ground) retains the same relationship to itself because it is not reliant on air pressure to move a needle on a gauge in the cockpit.

Thus 300mph at sea level will show 300 mph on the speedometer gauge where 300 mph at 10,000 ft. will show a lower airspeed on the speedometer gauge.

2. Most of these aircraft are faster at higher altitudes above sea level. Exactly what altitude will vary from one plane to another, depending on supercharger impellors, whether the engine has single stage or 2 stage supercharging, manifold design and compression ratios, etc..

When you read that a plane has a maximum speed of "xxx km/h" this is almost always at an altitude above 3,000m, for some it might be as high as 6 or even 7 thousand meters. I'm generalizing to illustrate the point, the specifics are all taken into account when we model the individual aircraft.

I'd go as far as to say, without checking any charts ... that NONE of the planes in the game record their maximum speeds at sea level.

[eigenman]

1. Airspeed at sea level is the only altitude where IAS (indicated air speed, being that displayed on the gauge) is virtually the same as TAS (true air speed, being your actual speed across the ground) ... as altitude increases above sea level the decrease in air pressure causes IAS to reduce (as the air pressure forced down the pitot tube that drives the speedometer gauge decreases with altitude) while your TAS (the real speed you are going across the ground) retains the same relationship to itself because it is not reliant on air pressure to move a needle on a gauge in the cockpit.

Thus 300mph at sea level will show 300 mph on the speedometer gauge where 300 mph at 10,000 ft. will show a lower airspeed on the speedometer gauge.

2. Most of these aircraft are faster at higher altitudes above sea level. Exactly what altitude will vary from one plane to another, depending on supercharger impellors, whether the engine has single stage or 2 stage supercharging, manifold design and compression ratios, etc..

When you read that a plane has a maximum speed of "xxx km/h" this is almost always at an altitude above 3,000m, for some it might be as high as 6 or even 7 thousand meters. I'm generalizing to illustrate the point, the specifics are all taken into account when we model the individual aircraft.

I'd go as far as to say, without checking any charts ... that NONE of the planes in the game record their maximum speeds at sea level.

That makes sense DOC. I didn't account for higher TAS at higher altitude. Higher TAS because there is less drag.

[eigenman]

So off the cuff without an E6B I'll say there is a bout a 2% increase per 1000 feet of altitude MSL which I'm going to bet will put us around the max speed listed of the dewo at 3KM considering IAS will be lower at that altitude. I'm not looking for pure accuracy, I was just off so much that I had to be missing a parameter and drag was the factor. Man I need to file flight plans again some day because I've clearly lost some knowledge by just getting in a plane and flying.

[OLDZEKE]

1st off make sure your throttle is giving 100% boost.

I got 460 indicated at sea level with h75.

And indicated does change/read lower than actual at higher alts.

And I think h75s best alt for speed is 3k, and pretty sure it's above the game listed max speed at 3k alt.

Edited May 15, 2012 by OldZeke

[Tigger6]

No I was just using IAS at sea level which should be as close to TAS as needed since there is no wind and temperature is a constant 10 degrees C. I'm not sure the distances are scaled correctly enough in the game to actually measure a ground speed.

I guess I should just test all planes and see if they are all that off at sea level. If so then there is a parameter I'm missing.

Distances are scaled correctly- the usual way to measure GS is to go parallel to a grid square side and measure the time it takes to cross the grid (which is 16km long). Done properly you get airspeed accurate to about 0.5 km/h.

[eigenman]

Distances are scaled correctly- the usual way to measure GS is to go parallel to a grid square side and measure the time it takes to cross the grid (which is 16km long). Done properly you get airspeed accurate to about 0.5 km/h.

Hmm never actually tried it. No point in computing TAS if this works.