190A5 vs 190A8

[Ardy123]

HiTech,
What is the engine output of the A8 as its modeled in the game?

Thanks

[FLS]

And, not to highjack (this is related) over to D-9 but I read today that 426 mph at ~19k is top speed for a D-9 w/o the MW50 injection. The source cited 438 as top speed for the D-9 with...

I recall reading the early A-series had problems with overheating under boost and that the D-9's Jumo's suffered from scarcity of MW-50 systems.

So, I think the power issue would be a good one for the HTC boys to illuminate.

Besides, as you note, it beats trying to illuminate outer space.

I believe the 426 MPH D-9 is with the Jumo 213A injected engine and the 435 MPH D-9 is with the DB 603 injected engine.

[Badboy]

Gaston,

I think I can offer a more plausible explanation for why we see pilots referring to improving their turn by throttling back.

When we consider an aircraft performance envelope as illustrated by a Energy Maneuverability diagram, it is normally bounded by a lift limit on the left, which is in effect a stall line, by a G limit at the top, which for real aircraft would be a structural limit, and would depend on configuration, external stores etc, and a placard limit on the right.

I've drawn a diagram below for an aircraft with the following data:

Weight: 8000lbs
Wing Area: 200ft^2
Engine: 1600HP
Clmax: 1.4

It has the normal lift limit, a top speed limit on the right instead of a placard limit, and instead of using a structural G limit I've used a G limit associated with pilot physiology.



Regarding that G limit, according to one WWII fighter pilot he would begin to lose peripheral vision at 4 to 4.5G and holding that for as little as 10 seconds would cause complete loss of vision. Not blackout, he was still aware and could still feel, he just couldn't see anything. If a pilot without a G suit couldn't hold as much as 4.5G for long without losing sight of the enemy, I suggest that would be a more likely self imposed limit. So the diagram above is drawn with that limit and if the pilot wanted to stay in a hard turn for a significant period of time, he would probably have to remain closer to 4 than 4.5G.

That would mean that the best turn or corner velocity would occur at between 210 and 225mph. The negative Ps at those corner velocities indicate that 4 to 4.5G turns could be sustained with an altitude loss of between 1800 and 2700 fpm respectively.

That I suspect may be an explanation for the anecdotes we have seen that refer to reducing throttle. For the diagram I posted above, a pilot who could only hold 4g for an extended period of time without losing sight of the enemy, would need to be at about 210mph to achieve his best turn, and it could be sustained with an altitude loss of about 1800 fpm. So if he was any faster than that he would benefit from throttling and I suspect entering an engagement above that speed was common.

Of course, late war G suits pushed those G limits up to 5.5 to 6G and aircraft with inclined seats and high foot positions helped too.

However, it is of course still wrong to say that an aircraft has a better sustained turn at anything less than full power, and I think it is much more likely that the G tolerance of real pilots may have compelled them to reduce speed to achieve their best turn, as explained above, and that appears to be consistent with the anecdotes we have seen.

Badboy

[Wmaker]

Ardy, I'd like to add that 1800ps figure comes from performance chart for BMW 801D Sr.Nr. 9-801:5401 dated 10.7.42 and is for the 1.42ata@2700rpm setting. The 1.58ata-setting, which was accomplished with ADI (C3-injection), developed more power.

[Ardy123]

Ardy, I'd like to add that 1800ps figure comes from performance chart for BMW 801D Sr.Nr. 9-801:5401 dated 10.7.42 and is for the 1.42ata@2700rpm setting. The 1.58ata-setting, which was accomplished with ADI (C3-injection), developed more power.

hmm, so if the A-8 is engine performance is modeled to that document then it should be outputting  2021.92hp, now the only thing missing is the confirmation that it was modeled from that document or that the modeling is treating 1.58 ata as 2021.92 hp.

This would mean that the power to weight ratio for both the A5 and A8 is...
A8 = 9702lb / 2021.92hp ~= 4.7984lb per hp
A5 = 8802lb /  1676.71hp ~= 5.249lb per hp

I would expect the A8 to have better climb performance than the A5  and acceleration given that it has more power per lb of weight, this is not reflected in the game. What am I missing?

[Ack-Ack]

hmm, so if the A-8 is engine performance is modeled to that document then it should be outputting  2021.92hp, now the only thing missing is the confirmation that it was modeled from that document or that the modeling is treating 1.58 ata as 2021.92 hp.

This would mean that the power to weight ratio for both the A5 and A8 is...
A8 = 9702lb / 2021.92hp ~= 4.7984lb per hp
A5 = 8802lb /  1676.71hp ~= 5.249lb per hp

I would expect the A8 to have better climb performance than the A5  and acceleration given that it has more power per lb of weight, this is not reflected in the game. What am I missing?

I think at this point in this thread, you're probably better of creating another thread just on the engine used so your questions won't continued to get buried under the other topics being discussed.


ack-ack

[Ardy123]

I think at this point in this thread, you're probably better of creating another thread just on the engine used so your questions won't continued to get buried under the other topics being discussed.


ack-ack

Good idea
http://bbs.hitechcreations.com/smf/index.php/topic,287701.0.html

[PJ_Godzilla]

That would mean that the best turn or corner velocity would occur at between 210 and 225mph. The negative Ps at those corner velocities indicate that 4 to 4.5G turns could be sustained with an altitude loss of between 1800 and 2700 fpm respectively.

This looks like a pretty sound analysis. My only question comes in regard to the statement above. Clearly, that 4.5g turn is unsustainable from the graph posted. How were you able to quantify the alt loss as you did? I see a radius and g diff b/w best and best sustained but cannot see how you estimated the alt loss.

[hitech]

Godzilla was this your question?

(drag - thrust) * speed = Needed Power.

Weight * decent rate = Power.

HiTech

Changed had drag and trust reversed in subtraction.

[PJ_Godzilla]

THE MAN nails it with equation 2...

I think. Let me bounce this off you. T-D also = MA. I.e., an a/c entering a turn it CANNOT sustain will decel because drag will exceed thrust. This decel will continue until required power = available power - and we end up on the sustained turn line.

Going back to the power deficit, (back into Force time velocity - same as an energy per unit time) I'd say we can safely assume that the power deficit in the instantaneous turn will translate into the power of the fall, as you couch it in eqn. 2.

As for the sign convention, who cares about that?

[hitech]

As for the sign convention, who cares about that?

I don't care hence why I had it reversed. All the same to me, I just think the difference.

And yes about instantaneous turn it either shows up as -accelerate or loss in alt. And hence why E = V^2 + Alt.

HiTech

[Badboy]

This looks like a pretty sound analysis. My only question comes in regard to the statement above. Clearly, that 4.5g turn is unsustainable from the graph posted. How were you able to quantify the alt loss as you did? I see a radius and g diff b/w best and best sustained but cannot see how you estimated the alt loss.

I normally post EM diagrams without a full set of curves showing specific excess power, or Ps curves. I normally just show the zero Ps curve because that shows the aircraft's sustained turning ability. If you want to see how the aircraft can gain or lose energy you need all the Ps curves, and I've included them in the diagram below. The units are in feet per second. 



You can see from this diagram that when the aircraft is at the 4.5G corner velocity of 225mph it has negative Ps of 46ft/s and that means that in order to maintain that optimum turn the aircraft would need to descend at 2760ft/min. Otherwise it will decelerate at the rate of 3.1 mph every second.

You also see that at the 4G corner velocity of 212mph it has negative Ps of 28ft/s and the aircraft would need to descend at the rate of 1680ft/min in order to maintain that turn, if the aircraft stayed level it would decelerate at the rate of 2 mph every second.

That means a pilot on the edge of grey out could maintain his optimum rate and radius in a 8 degree descending spiral turn at the 4.5G corner, or a 5 degree descending spiral turn at the 4G corner, as shown in the diagram below. 



I've used P-51 images to create the diagram because I had them handy, but the EM diagrams are for the generic aircraft data I posted earlier, not the P-51. Also this diagram isn't drawn to scale, so the spiral turn looks steeper than it should.

What this means is that in this case, a pilot entering a fight at some speed significantly above 225mph and who wanted to perform a maximum rate turn within his physiological G limits, might choose to do it by reducing throttle until his speed was between 212 and 225 mph. Remember, if he can only pull 4.5G for about ten seconds before losing his vision, any time he spends flying faster than his 4.5G corner velocity will be time spent turning at less than optimum conditions, and that means allowing an adversary to gain on him in the turn. So it is hardly suprising that there are anecdotes describing just that. However, once they reach their 4G or 4.5G corner velocity (depending on the particular pilots G tolerance) their best option would be to try to maintain that optimum turn for as long as possible. That means going to full power! But even at full power, they couldn't maintain that turn, they would need to exchange altitude for it by entering a descending spiral turn with an angle of descent of between 5 and 8 degrees, so a relatively shallow descent.  You can see from the EM diagram that staying level and allowing the aircraft to decelerate to its best sustained turn may not have been the preferred option. Firstly because the best sustained turn rate is about 20dps but it can achieve 23dps and 24.5dps at the 4G and 4.5G limits respectively, and when you consider that a 2dps advantage was considered decisive, that extra turn rate is very significant. But also because I suspect that real pilots were less willing to ride the edge of the stall, and that maintaining speed close to corner velocity, albeit a corner velocity defined by their own G tolerance, would give them more options as well as the best instantaneous turn for as long as the altitude lasted, and so I think that would have been a more desirable choice.

Badboy
 

[Gaston]

Gaston, it doesn't matter how you try to justify it, the idea that sustained turn performance improves by reducing throttle is wrong. So any conclusions you reach based on that idea will also be wrong.

Just to be clear, allow me to spell it out:

If you consider any aircraft at any speed, in otherwords across the entire envelope, the sustained turning performance will always be maximised at full power. Reduce throttle and the sustained turning performance will also reduce.

Saying that it works the other way around, will never make it so, regardless of how many anecdotes you misinterpret.

Badboy

   -I love the part about ANY aircrafts... Props and jets are exactly the same folks: Remember that... It kind of reminds me of my gape-mouthed reading of Shaw's fighter tactics book, which showed not the slightest glimmer of understanding of the difference between TRACTION and PROPULSION: You have to wonder why engineers even bother using those terms... Most of the WWII anecdotal examples he produced unsurprisingly involved the P-47, which is probably the most likely prop aircraft to produce accounts flattering to his near-total lack of practical understanding of actual WWII air fighting (shared by a lot of US Navy test pilots apparently)... Of course, with the P-51, he carefully omitted the numerous successful accounts of low-speed downthrottling/coarse prop pitch/popped flaps that would show how inapplicable much of his theories are to real prop-driven combat...(You think the Hanseman account I use is the only one? It is merely the most obvious one of about a half-dozen in Mike William's WWII site, and several more elsewhere: If that one doesn't do it, NOTHING will...).

    Your argument basically amounts to, I put a bigger number into an equation, and therefore a bigger outcome is necessary in real-life as it is in the equation... Has it occurred to you that turning inefficiency can drastically increase with more power? And that several different aces from several nations have mentionned downthrottling as an essential part of dogfighting? Off the top of my head, Karhila said:

    ""I learned to fly with the "Cannon-Mersu" (MT-461). I found that when fighter pilots got in a battle, they usually applied full power and then began to turn. In the same situation I used to decrease power, and with lower speed was able to turn equally well. I shot down at least one Mustang (on 4th July 1944) in turning fight. I was hanging behind one, but I could not get enough deflection. Then the pilot made an error: he pulled too much, and stalling, had to loosen his turn. That gave me the chance of getting deflection and shooting him down. It was not impossible to dogfight flying a three-cannon Messerschmitt."
" When the enemy decreased power, I used to throttle back even more. In a high speed the turning radius is wider, using less speed I was able to out-turn him having a shorter turning radius. Then you got the deflection, unless the adversary did not spot me in time and for example banked below me. 250kmh seemed to be the optimal speed."

   -But of course this 32 victory ace doesn't know what he is talking about... And note also the funky 160 MPH optimal sustained turn speed for a Me-109G-6... That's as close as possible to the "Corner Speed" of course...

   http://www.virtualpilots.fi/feature/articles/109myths/#g6r6

   Let's see an interpretation of this...

   Gaston

   P.S. I got a bit behind on your interesting later posts, so I will reply to those later...

   G.

[Ardy123]

Wit words you speak, and tone you set, ya shall be forewarned, I sense a PNG in someones future....

[Guppy35]

  -I love the part about ANY aircrafts... Props and jets are exactly the same folks: Remember that... It kind of reminds me of my gape-mouthed reading of Shaw's fighter tactics book, which showed not the slightest glimmer of understanding of the difference between TRACTION and PROPULSION: You have to wonder why engineers even bother using those terms... Most of the WWII anecdotal examples he produced unsurprisingly involved the P-47, which is probably the most likely prop aircraft to produce accounts flattering to his near-total lack of practical understanding of actual WWII air fighting (shared by a lot of US Navy test pilots apparently)... Of course, with the P-51, he carefully omitted the numerous successful accounts of low-speed downthrottling/coarse prop pitch/popped flaps that would show how inapplicable much of his theories are to real prop-driven combat...(You think the Hanseman account I use is the only one? It is merely the most obvious one of about a half-dozen in Mike William's WWII site, and several more elsewhere: If that one doesn't do it, NOTHING will...).

    Your argument basically amounts to, I put a bigger number into an equation, and therefore a bigger outcome is necessary in real-life as it is in the equation... Has it occurred to you that turning inefficiency can drastically increase with more power? And that several different aces from several nations have mentionned downthrottling as an essential part of dogfighting? Off the top of my head, Karhila said:

    ""I learned to fly with the "Cannon-Mersu" (MT-461). I found that when fighter pilots got in a battle, they usually applied full power and then began to turn. In the same situation I used to decrease power, and with lower speed was able to turn equally well. I shot down at least one Mustang (on 4th July 1944) in turning fight. I was hanging behind one, but I could not get enough deflection. Then the pilot made an error: he pulled too much, and stalling, had to loosen his turn. That gave me the chance of getting deflection and shooting him down. It was not impossible to dogfight flying a three-cannon Messerschmitt."
" When the enemy decreased power, I used to throttle back even more. In a high speed the turning radius is wider, using less speed I was able to out-turn him having a shorter turning radius. Then you got the deflection, unless the adversary did not spot me in time and for example banked below me. 250kmh seemed to be the optimal speed."

   -But of course this 32 victory ace doesn't know what he is talking about... And note also the funky 160 MPH optimal sustained turn speed for a Me-109G-6... That's as close as possible to the "Corner Speed" of course...

   http://www.virtualpilots.fi/feature/articles/109myths/#g6r6

   Let's see an interpretation of this...

   Gaston

   P.S. I got a bit behind on your interesting later posts, so I will reply to those later...

   G.

The danger of the anectodal stuff is you are adding the ability of the pilot involved to the equation.  What the 32 kill Ace could do in a 109 may be completely different from a novice.   I post my favorite 38 combat report all the time and it involves a 38J pilot still carrying his 500 pounders, out turning a 109G in a fight on the deck after being bounced by the higher 109.  If that's my evidence then I can claim that a P38J carrying 500 pounders should out turn a 109 every time.  My guess is however that it isn't the case.