F-14 low speed prowess vs Other Aircraft

[captain_dalan]

You know, i can try to extract some L/D values based on this chart and try to adapt them for lower altitudes, but the configuration is just not as comparable to anything we've been using so far.

[Hummingbird]

You absolutely have no idea what you're talking about to make such a patently false statement, and this is explicitly the reason why I've been stating that USAF manuals are deficient in providing the Ps compared to the doghouse. We're not discussing *sustained turns*: we're discussing a turn in which induced drag will pull the aircraft through CV- right at the top of the plot.

 

Fine, start at Mach .8/3000' radius. By the time you're complete at Mach .5 (or thereabouts), your actual radius will be below 2500'. And that's at 15k; bring it down to SL, and you're talking sub-2000' radii with a turn rate in excess of 20+ dps.

 

Nah, F-15 can't do that.

 

If we're not discussing *sustained turns*, then why was a chart describing "sustained level turns" brought up?

[lunaticfringe]

Because it's the only one AVAILABLE IN THE F-15C'S -1.

 

We've been talking about this fact for over two pages already- keep up.

[Hummingbird]

Because it's the only one AVAILABLE IN THE F-15C'S -1.

 

We've been talking about this fact for over two pages already- keep up.

 

I think the problem is that you dropped into a conversation between GG and I, because I was addressing a couple of claims he made earlier.

 

Do you agree that an F-15 could achieve its' min radius turn in 15 sec? A whole 1.5 sec faster than an A6M2 Zero with a wing loading of 22 lb/ft^2 could do its fastest turn?

[captain_dalan]

I think the problem is that you dropped into a conversation between GG and I, because I was addressing a couple of claims he made earlier.

 

Do you agree that an F-15 could achieve its' min radius turn in 15 sec? A whole 1.5 sec faster than an A6M2 Zero with a wing loading of 22 lb/ft^2 could do its fastest turn?

The question can be a bit misleading yes. But even though it may not seam like that at first, modern fighters can actually turn a lot "quicker" then WW2 fighters.

[lunaticfringe]

I think the problem is that you dropped into a conversation between GG and I, because I was addressing a couple of claims he made earlier.

 

I think the problem is that a bunch of us have been saying the same thing regarding the data, while you regard this topic as a PM between you and GG rather than a discussion on a public forum.

 

Do you agree that an F-15 could achieve its' min radius turn in 15 sec? A whole 1.5 sec faster than an A6M2 Zero with a wing loading of 22 lb/ft^2 could do its fastest turn?

 

Looking at what it will do at 15k (20+ degrees per second passing through corner) I wouldn't be surprised at all if it got real close at either 10k, 5k, or SL and the right configuration.

[Hummingbird]

The question can be a bit misleading yes. But even though it may not seam like that at first, modern fighters can actually turn a lot "quicker" then WW2 fighters.

 

I've never seen or heard of an F-15 doing a 360 in 15 sec, be it at airshows, in videos or from talking to actual pilots.

 

Common concensus seems to be 21-22 sec to do a 360 at SL in clean configuration.

[GGTharos]

I think it's funny that you believe wing loading is somehow the one number that means anything here.

I also think it's funny that you're describing a turn made without any other characteristics, such as: Altitude the turn was made at, gross weight of the aircraft, entry airspeed and exit airspeed (ie ... what technique was used to execute the turn).

 

Like lunaticfringe said: Try to keep up. Turn radius is a relationship between G loading ( ... also known as turn rate) and speed - wing loading tends to determine the speed at which you can sustain a certain amount of G given a certain amount of thrust. Wing loading will also usually determine the intantaneous turn rate capability, but that's a very simplistic view of things.

 

I think the problem is that you dropped into a conversation between GG and I, because I was addressing a couple of claims he made earlier.

 

Do you agree that an F-15 could achieve its' min radius turn in 15 sec? A whole 1.5 sec faster than an A6M2 Zero with a wing loading of 22 lb/ft^2 could do its fastest turn?

[Hummingbird]

I think the problem is that a bunch of us have been saying the same thing regarding the data, while you regard this topic as a PM between you and GG rather than a discussion on a public forum.

 

Thing is I specifically qouted and answered him sir, thus I find your aggressive attitude unwarranted.

 

 

Looking at what it will do at 15k (20+ degrees per second passing through corner) I wouldn't be surprised at all if it got real close at either 10k, 5k, or SL and the right configuration.

 

But would it achieve the smallest possible turn radius then?

[captain_dalan]

I've never seen or heard of an F-15 doing a 360 in 15 sec, be it at airshows, in videos or from talking to actual pilots.

 

Common concensus seems to be 21-22 sec to do a 360 at SL in clean configuration.

Why not? If a clean, very lightly loaded F-15 could say peak at 28deg/s and start it's turn at say 18deg/s, depending on the bleed rate it could easily average a 24deg/s. We don't have the charts needed to "prove" this directly, but a good quality AFM can act as our on board simulator.

[Hummingbird]

I think it's funny that you believe wing loading is somehow the one number that means anything here.

I also think it's funny that you're describing a turn made without any other characteristics, such as: Altitude the turn was made at, gross weight of the aircraft, entry airspeed and exit airspeed (ie ... what technique was used to execute the turn).

 

I did this because YOU described a 15 sec turn committing the very same sin ^^

 

Like lunaticfringe said: Try to keep up. Turn radius is a relationship between G loading ( ... also known as turn rate) and speed - wing loading tends to determine the speed at which you can sustain a certain amount of G given a certain amount of thrust. Wing loading will also usually determine the intantaneous turn rate capability, but that's a very simplistic view of things.

 

Oh I know this, but I don't think the F-15 enjoys a CL_max advantage over the straight winged A6M2 to be honest, considering thickness & aspect ratios etc. Either way it would have to be an enormous advantage to make up the disadvantage in wing loading ;) Obviously the F-15 enjoys a big TW advantage, but it still needs wing to turn ^^

 

In short the A6M2 no doubt is capable of turning tighter and faster than an F-15 in a sustained turn

[lunaticfringe]

Thing is I specifically qouted and answered him sir, thus I find your aggressive attitude unwarranted.

 

Yeah, and then you started answering me. That generally requires one having been paying attention to what was being said.

 

But would it achieve the smallest possible turn radius then?

 

For that rate around 360 degrees you're desperate for? Yes.

 

See, this is what's funny: you want it one way (minimum radius) or the other (< 16 seconds).

 

If you're going to get nuts over 200' of radius above CL Max when the machine tears your target number up- I hate to tell you: when you have that much turning ability to spare, 200' of radius ain't saving you.

[Hummingbird]

Why not? If a clean, very lightly loaded F-15 could say peak at 28deg/s and start it's turn at say 18deg/s, depending on the bleed rate it could easily average a 24deg/s. We don't have the charts needed to "prove" this directly, but a good quality AFM can act as our on board simulator.

 

But 28 deg/sec is only achievable in instantanous turn rate, and this bleeds energy/speed quickly.

[GGTharos]

I did this because YOU described a 15 sec turn committing the very same sin ^^

 

I described a turn you can experiment with by yourself.

 

Oh I know this, but I don't think the F-15 enjoys a CL_max advantage over the straight winged A6M2 to be honest, considering thickness & aspect ratios etc. Either way it would have to be an enormous advantage to make up the disadvantage in wing loading ;)

 

In short the A6M2 no doubt is capable of turning tighter and faster than an F-15 in a sustained turn

 

What does that have with an F-15 completing a 360 in 15 sec?

 

Completing a 360 in 15sec is a function of turn rate, not a function of wing loading. Wing loading factors in, but so does thrust and speed.

 

We already know an F-15 has no problem completing a 360 in under 20 sec using a sustained g turn.

Want to do it faster? Use instantaneous turn rate.

[captain_dalan]

But 28 deg/sec is only achievable in instantanous turn rate, and this bleeds energy/speed quickly.

Indeed, that is why you start the turn above corner and then bleed your way to it. The trick is to complete your turn right as you peak and not before.

[GGTharos]

Who cares? If I want to bleed speed and I can do it and still be in my corner band and keep a tight radius, who's stopping me? That's what we're talking about when we use the words 'depends on technique'.

 

But 28 deg/sec is only achievable in instantanous turn rate, and this bleeds energy/speed quickly.

[Hummingbird]

I would love to see a 15 sec 360 by an F-15.

[captain_dalan]

I would love to see a 15 sec 360 by an F-15.

If it means something to you, an F-14 could probably do it as well. I mean, even a loaded F-14A can sustain 18deg/s at SL and that would give it 20s to perform a full 360 degree turn. So if you bleed above corner, you should easily do it in less then 20s. Especially in a clean configuration.

 

However if an airshow imposes let's say a 6g limit, then this takes on a new dimension. Under those conditions, the plane that can pull those 6g at the lowest possible mach, will end up doing it in the least time. I think this is what GGT is saying all the time.

[Hummingbird]

If it means something to you, an F-14 could probably do it as well. I mean, even a loaded F-14A can sustain 18deg/s at SL and that would give it 20s to perform a full 360 degree turn. So if you bleed above corner, you should easily do it in less then 20s. Especially in a clean configuration.

 

However if an airshow imposes let's say a 6g limit, then this takes on a new dimension. Under those conditions, the plane that can pull those 6g at the lowest possible mach, will end up doing it in the least time. I think this is what GGT is saying all the time.

 

I've seen F-16's do 9 G turns at airshows and it took them longer than 15 sec to complete their min radius 360 turns :)

 

The clean F-16 is definitely more nimble than the clean F-14 or F-15 :)

Edited March 15, 2015 by Hummingbird

[captain_dalan]

Just because it was a 9g turn it doesn't mean it was the tightest or the quickest turn. It's often hard to estimate it "by eye". Was the g sustained during the entire turn? If not, how long was it sustained? What was the entry speed? The exit speed?

[Hummingbird]

Just because it was a 9g turn it doesn't mean it was the tightest or the quickest turn. It's often hard to estimate it "by eye". Was the g sustained during the entire turn? If not, how long was it sustained? What was the entry speed? The exit speed?

 

It's quite easy to time actually :) Now seeing as they call it a minimum radius turn I'd assume that means that they're giving it all they've got for what'ever speed they're going.

 

As for entry speeds, I obviously don't know, but it was definitely well above the corner speed.

[GGTharos]

How do you know if it was 'definitely above corner' then?

 

Above corner you sacrifice both STR and ITR, so you won't be turning anywhere near as quick as you would otherwise.

 

There are demonstration limitations that the USAF imposes on their demo teams, with entry and exit speeds and other parameters. They are published, and they're probably just a google away.

[captain_dalan]

It's quite easy to time actually :) Now seeing as they call it a minimum radius turn I'd assume that means that they're giving it all they've got for what'ever speed they're going.

 

As for entry speeds, I obviously don't know, but it was definitely well above the corner speed.

I didn't mean difficult to time the turn, but to estimate how much g's the AC is pulling throughout.

 

But... no need to ponder on that one. I have in front of me the F-16C block32 E-M charts and they do include the CLmax line. I can tell you that a clean F-16C at SL peaks at "only" 24.8 deg/s and has a best sustained turn at 21.5deg/s. This means the average quickest turn might actually be less then the Eagle's or very similar to it. Despite the size, this may be because the F-16 is alpha limited, so "quicker" turns although aerodynamically possible are just not available.

Edited March 15, 2015 by captain_dalan

[Hummingbird]

I didn't mean difficult to time the turn, but to estimate how much g's the AC is pulling throughout.

 

But... no need to ponder on that one. I have in front of me the F-16C block32 E-M charts and they do include the CLmax line. I can tell you that a clean F-16C at SL peaks at "only" 24.8 deg/s and has a best sustained turn at 21.5deg/s. This means the average quickest turn might actually be less then the Eagle's or very similar to it. Despite the size, this may be because the F-16 is alpha limited, so "quicker" turns although aerodynamically possible are just not available.

 

A clean F-15C @ 37,000 lbs has a best sustained turn rate of 20.5 deg/sec at SL, so that's 1 deg/sec slower than the F-16C.

 

Would be interesting to see the best sustained turn rate for a clean F-14 at SL.

[captain_dalan]

That might actually be something we will have to figure out the old fashioned way..... By doing it our selves once this module is out :)