Dora vs Mustang: Turning

[Hummingbird]

As I already mentioned: With lift comes drag.

 

As such the higher the lift coefficient the more drag the aircraft has to overcome to maintain speed, therefore it comes logically that the aircraft with the higher excess thrust will be able to maintain a constant speed (and therefore turn rate) at higher lift coefficients.

[Yo-Yo]

Yo Yo,

 

I am not talking about flight at CL_Max, which matters more to the short term turn rate, I am talking about the best sustained turn rate (i.e. the rate of turn that can be held indefinitely), where thrust matters as much as lift - as everything else being equal more thrust means that a higher lift coefficient can be maintained without losing speed. (With lift comes drag)

 

Also if I am reading your chart correctly it seems as though the heavier aircraft has the same turn rate as the lighter one at speeds below 330 km/h, and that makes very little sense now doesn't it?

 

Allow me to refer to page 53 section 6.38:

http://www.aviation.org.uk/docs/flighttest.navair.navy.milunrestricted-FTM108/c6.pdf

 

The document you refer to is for jets. The jet thrust generally is almost constant or even grows with the speed. Prop thrust has 1/V shape for the speed we are talking about.

That's why the best RoT is very different for the jets and props. Classic jet with low bypass ratio or AB jet will have the best RoT not at the point of intersection CL_max curve and thrust = drag curve but somewhere at the thrust=drag curve. Exactly as your doc shows at 6.23.

 

For props and high bypass ratio jets dashed line at 6.23 will be monotone descending, so - see my statement above - the best RoT will be at the intersection of the instanteneous turn (Max CL) line and dashed drag = thrust line. As the power (thrust) changes the best RoT point will slide along the instanteneous curve.

 

 

The difference between prop and jet thrust is the reason of very different shape of sustained turn curves for prop and jets - prop plane has very sharp peak for the best turn rate and the jet has smooth.

Edited August 13, 2014 by Yo-Yo

[Hummingbird]

The document you refer to is for jets. The jet thrust generally is almost constant or even grows with the speed. Prop thrust has 1/V shape for the speed we are talking about.

That's why the best RoT is very different for the jets and props. Classic jet with low bypass ratio or AB jet will have the best RoT not at the point of intersection CL_max curve and thrust = drag curve but somewhere at the thrust=drag curve. Exactly as your doc shows at 6.23.

 

For props and high bypass ratio jets dashed line at 6.23 will be monotone descending, so - see my statement above - the best RoT will be at the intersection of the instanteneous turn (Max CL) line and dashed drag = thrust line. As the power (thrust) changes the best RoT point will slide along the instanteneous curve.

 

 

The difference between prop and jet thrust is the reason of very different shape of sustained turn curves for prop and jets - prop plane has very sharp peak for the best turn rate and the jet has smooth.

 

I have a feeling that we're talking past each other here :hmm:

 

I know and understand that jet engine thrust & propeller thrust curves are not similar, as you say jet engine thrust stays pretty much constant regardless of speed, where'as prop thrust drops off with increases in speed:

 

 

However that is really besides the point I am trying to make as both the A8 & D9 are prop planes and as such they will experience the same drop off in thrust as speed increases, thus their percentage wise difference in thrust should stay somewhat the same.

 

The point I am trying stress is that the lowest speed at which a certain amount of G's can be held indefinitely should become lower with any increase in thrust - limited by the critical AoA and minimal speed at which the aircraft can stay in the air of course.

 

In other words an increase in thrust should enable an increased maintainable speed at any AoA pulled up until the critical AoA.

Edited August 13, 2014 by Hummingbird

[Yo-Yo]

I have a feeling that we're talking past each other here :hmm:

 

I know and understand that jet engine thrust & propeller thrust curves are not similar, as you say jet engine thrust stays pretty much constant regardless of speed, where'as prop thrust drops off with increases in speed:

 

 

However that is really besides the point I am trying to make as both the A8 & D9 are prop planes and as such they will experience the same drop off in thrust as speed increases, thus their percentage wise difference in thrust should stay somewhat the same.

 

The point I am trying stress is that the lowest speed at which a certain amount of G's can be held indefinitely should become lower with any increase in thrust - limited by the critical AoA and minimal speed at which the aircraft can stay in the air of course.

 

In other words an increase in thrust should enable an increased maintainable speed at any AoA pulled up until the critical AoA.

 

We are talking about MAXIMAL RoT, aren't we? Point 1 is the best RoT for the less power, point 2 - for the increased power.

[theChris]

Excuse me for buting in, but i think Hummingbird is talking sustained turn at lower speeds then optimal (i.e. pushing your plane to the limit in a turn like almost everyone will do in a turn fight to avoid being sliced within the few seconds of an engagement).

 

In a prolonged fight you are better off having more thrust as you can maintain a higher aoa then the slower accelerating enemy who has to decrease aoa to decrease induced drag so that he does not stall.

[Hummingbird]

Excuse me for buting in, but i think Hummingbird is talking sustained turn at lower speeds then optimal (i.e. pushing your plane to the limit in a turn like almost everyone will do in a turn fight to avoid being sliced within the few seconds of an engagement).

 

In a prolonged fight you are better off having more thrust as you can maintain a higher aoa then the slower accelerating enemy who has to decrease aoa to decrease induced drag so that he does not stall.

 

Bingo!

[Solty]

Hmmm... as far as I know (correct me if I am wrong) if you want to acheive more thrust at low speed and altitude, you have to add more power to the engine (it will give the propeller more 'RPM' and increase thrust). The more power, the quicker the movment of the propeller and that increases the torque. High torque is bad for maintainting a turn as it rotates the plane. The lighter the plane and more powerfull the engine, the more problematic it will be during tight turning at low speed. Right?

[Kwiatek]

What i have seen during my online combat in P-51 against Fw 190 D-9 i found that some D-9 pilots could keep with my P-51 in turn. And i think i could turn my P-51 quite efficently.

 

Also im sure that D-9 with actual power rating, better roll rate is general better dogfighter then P-51. Not mention that is also faster and better climber at low to medium alts.

 

Most adventages is on the D-9 side.

[theChris]

Hmmm... as far as I know (correct me if I am wrong) if you want to acheive more thrust at low speed and altitude, you have to add more power to the engine (it will give the propeller more 'RPM' and increase thrust). The more power, the quicker the movment of the propeller and that increases the torque. High torque is bad for maintainting a turn as it rotates the plane. The lighter the plane and more powerfull the engine, the more problematic it will be during tight turning at low speed. Right?

 

Yes more power more torque, which also means faster roll rate at low speeds too (while rolling with the torque). In general planes turn better in the direction of their torque. What i mean is you won't be fighting in the vertical at near stall speeds.

 

That being said the 300-400hp difference (or whatever it is exactly, it changes depending on alt) shouldn't make too much difference anyway, and a good pilot will naturally counter the torque with ailerons at constantly changing speeds.

[gavagai]

Yes more power more torque

 

T(Nm)∗ω(rpm)=P(kW)

9549

 

Not necessarily.:smilewink:

 

Google power and torque and you'll find a lot of graphs where at some point torque is diminishing while power is increasing because of rpm.

[Yo-Yo]

T(Nm)∗ω(rpm)=P(kW)

9549

 

Not necessarily.:smilewink:

 

Google power and torque and you'll find a lot of graphs where at some point torque is diminishing while power is increasing because of rpm.

 

Not rpm, to be accurate - rad/s or sometimes s^(-1)

[Solty]

(i.e. pushing your plane to the limit in a turn like almost everyone will do in a turn fight to avoid being sliced within the few seconds of an engagement).

 

In a prolonged fight you are better off having more thrust as you can maintain a higher aoa then the slower accelerating enemy who has to decrease aoa to decrease induced drag so that he does not stall.

 

Yes more power more torque, which also means faster roll rate at low speeds too (while rolling with the torque). In general planes turn better in the direction of their torque. What i mean is you won't be fighting in the vertical at near stall speeds.

That being said the 300-400hp difference (or whatever it is exactly, it changes depending on alt) shouldn't make too much difference anyway, and a good pilot will naturally counter the torque with ailerons at constantly changing speeds.

 

:huh:Beeing in pure horizontal does not give you any kind of advantage over moving in vertical. At least you are grabbing a little bit of potential energy when going up and kinetic going down... In horizontal you are just burning it... I fail to see how nobody would go for a little dive or climb... unless you can't because you are at ground level... in that case... good luck :music_whistling:

[theChris]

:huh:Beeing in pure horizontal does not give you any kind of advantage over moving in vertical. At least you are grabbing a little bit of potential energy when going up and kinetic going down... In horizontal you are just burning it... I fail to see how nobody would go for a little dive or climb... unless you can't because you are at ground level... in that case... good luck :music_whistling:

 

Wing lift, nullified in the vertical.

 

While pulling up you will stall a wing DUE to engine torque at low speed (which is what i thought you were getting at with your previous comment)

 

You guys are right about the torque rolling thing, more rpm = more power more torque - more power given the other is constant. If power is increased at a constant torque the plane will still have a higher "torque" acting on it from the engine. :)

 

editL btw im just a student i don't claim to be a no it all. This is just what i understand

Edited August 20, 2014 by theChris

[Hummingbird]

What i have seen during my online combat in P-51 against Fw 190 D-9 i found that some D-9 pilots could keep with my P-51 in turn. And i think i could turn my P-51 quite efficently.

 

Also im sure that D-9 with actual power rating, better roll rate is general better dogfighter then P-51. Not mention that is also faster and better climber at low to medium alts.

 

Most adventages is on the D-9 side.

 

Yes, I believe this to be at odds with reality.

 

The Fw190 Dora-9 should be able to maintain a higher sustained turn rate than the P-51D Mustang at low to medium altitudes thanks to the extra power it has available at these altitudes, plus the near identical lift to weight ratio when both planes are at combat loads (60% fuel incase of the P-51).

 

This is backed up by the take off distance & landing speed figures for both aircraft as well, which are good indicators of sustained turn performance at those particular powersettings (TO power).

[Yo-Yo]

Yes, I believe this to be at odds with reality.

 

The Fw190 Dora-9 should be able to maintain a higher sustained turn rate than the P-51D Mustang at low to medium altitudes thanks to the extra power it has available at these altitudes, plus the near identical lift to weight ratio when both planes are at combat loads (60% fuel incase of the P-51).

 

This is backed up by the take off distance & landing speed figures for both aircraft as well, which are good indicators of sustained turn performance at those particular powersettings (TO power).

 

You do not take in account different CL especially at the speed the best turn ratio is. Mustang has better CL max at low M-numbers and much preferrable at medium.

[Der_Fred]

Reading through this topic is so much like Déjà vu :)

 

Nobody's actually bothered to :-

 

1) indicate the direction of the turn

2) the altitude of action

3) speeds

.. and...

4) Pilot reports are important, but must be interpreted correctly

 

Solty comes close with his points 1-3.., Point 4 I'd leave out.

 

There another characteristic of the FW that is mentioned in the Soviet assessments, the FW tend to 'sink' when elevator is applied aggressively.

This 'rotation' will most likely give the impression that the FW is out-turning the other a/c, but this is an important momentary attribute of the FW, as it enables you to give the other aircraft a deflection 'squirt' in a tight turn.

 

The fire power of the FW, will make this 'squirt' very effective, thus maybe giving the pilot a false sensation of the FW's turning ability.

After all, the only reports you hear of, are from surviving pilots.

 

Another thing is the the A5 was considered the most agile Fw190, followed by, I think the A9, then A8, which was more numerous.

 

I'll like to see a short nosed A5 or A9 sometime.

:)

[NineLine]

I'll like to see a short nosed A5 or A9 sometime.

:)

 

 

VEAO said they are doing one didnt they?

[Der_Fred]

Zzzzz ... Seeing is believing

[Der_Fred]

VEAO said they are doing one didnt they?

I'll definitely buy the radial FW190... it's a beaut to handle and can pull brilliant moves.

The Dora.. I have little interest in...

:)

[Stephen Higginbotham]

I'm a little disappointed in the performance of the P-51! It is like has the performance of a Cessna 150 cub plane! very weak

[USARStarkey]

It cant even get to its actual top speed. The thing get just barely hit 429mph at best alt-24k. It should be getting about 440mph at that or 26k.

[jermin]

VEAO said they are doing one didnt they?

 

Is there any link to read more about that?

[gavagai]

There another characteristic of the FW that is mentioned in the Soviet assessments, the FW tend to 'sink' when elevator is applied aggressively.

 

Also known as an uncoordinated turn IIRC.;)

[Solty]

Is there any link to read more about that?

+1 I was not able to see anything about it on their main page.

[Narushima]

http://forums.eagle.ru/showthread.php?t=127100