Air refueling KTAS?

[OutOnTheOP]

So I've been practicing aerial refueling lately, and I've noticed something: no matter what speed I assign to the KC-135 (both initial and waypoint speeds), it always proceeds through it's entire route at approximately 220 knots true airspeed.

 

This makes for a number of problems, I've noticed. At that low airspeed, the A-10 is RIGHT at the verge of flap deployment (if left on the default maneuver setting), so you have to manually set flaps to up, or else it will automatically start raising and dropping flaps, wildly changing your total velocity vector and trim settings when you least expect it. Not Good during A2A refueling. This problem is already resolved. I know. Set flaps to "up". Check, roger, hooah.

 

At this low airspeed, the A-10 also "wallows" around the sky a lot; control inputs have a decided lag from input to actual change in vector, very slight changes in engine RPM lead to large changes in pitch trim, and the aircraft tends to crab sideways a lot

 

I suspect refueling would be much, MUCH easier about 30-40 knots faster airspeed (250-260 KTAS).

 

Questions:

 

1) How (or can I) increase the tanker's airspeed?

2) On the assumption the refueling boom is only rated for a certain airspeed (which therefore dictates such low refueling speed), what is the real-world SOP speed for conducting aerial refueling?

 

*edit* everything I have found online seems to indicate that 280 KTAS is the "normal" refueling speed

*edit 2* everything I have found online indicates 220 KTAS is below the minimum accepted speed for refueling. Probably because it causes the same poor handling characteristics I have described above. The ones that are the issue at hand, which has nothing to do with flap settings.

Edited December 31, 2011 by OutOnTheOP

[FreeFall]

This makes for a number of problems, I've noticed. At that low airspeed, the A-10 is RIGHT at the verge of flap deployment, so you have to manually set flaps to up, or else it will automatically start raising and dropping flaps, wildly changing your total velocity vector and trim settings when you least expect it. Not Good during A2A refueling.

 

What? Excuse me, but I really am not sure what you are talking about. :confused:

[sobek]

This makes for a number of problems, I've noticed. At that low airspeed, the A-10 is RIGHT at the verge of flap deployment, so you have to manually set flaps to up, or else it will automatically start raising and dropping flaps, wildly changing your total velocity vector and trim settings when you least expect it. Not Good during A2A refueling.

 

The automatic flap retraction is only a safety mechanism to keep the flaps from being damaged. Pilot flap control is mandatory.

[OutOnTheOP]

Well... yes, but yhat's not the point. And as far as I can tell, the pilot CANNOT "manually" control flaps (IE, set them to "20 degrees"), you can only select "up", "maneuver", or "down"; maneuver and down both deploy and retract automatically at set airspeeds. I can have the switch set to "down" the entire flight, but the flaps will only deploy when airspeed drops below a certain level.

 

That's the problem; if the flaps automatically deploy at 190 IAS and the tanker is flying at 192, guess what that means? Any slight change of airspeed will cause your flaps to suddenly deploy or retract, which is a bad thing, because your aircraft will suddenly balloon up at a significant rate of ascent, and your trim will instantly go nose high. Neither are conducive to formation flight.

 

The solution to that one problem is obvious. In fact, I've already SOLVED the flaps problem, as I mentioned in my initial post: simply set them to the "up" position instead of the standard "maneuver". My point was that at that airspeed, you MUST select up (which means you will be very nose-high), because if you select any other flap setting, they will deploy and retract themselves at inopportune times.

 

The real issue is that flaps or no flaps, you end up flying a significant nose-up angle of attack, which means that any amount of roll (even a degree or two) causes a very significant sideways slip/crabbing. That's bad, because it makes it much more difficult to stay in formation. Which is the heart of the problem.

Edited December 31, 2011 by OutOnTheOP
removed ill-temperedness

[andyfoot]

After you take off, you have to manually retract your flaps. If you don't, they automatically retract (safety mechanism) as you increase speed (think it's around 195 - 200Kts, but not sure). Once your speed drops below that point again, your flaps will automatically extend again as the safety mechanism is reset and you still have your flaps set to extend.

 

The point is, that you should not rely on them automatically retracting/extending - that's a safety feature saving your Hog from damage because you are not using/forgot to use the correct procedure. You are causing your problem by trying to use flaps for a situation they are not designed or intended for.

Edited December 31, 2011 by andyfoot

[FreeFall]

After you take off, you have to manually retract your flaps.

 

Indeed. To be honest, I've never even imagined there would be some kinda automatic flap retraction at all. :P

[OutOnTheOP]

Please, no more comments about the flaps. I know. I KNOW you have to manually select "up" on the flap control switch.

 

The actual question: is it normal for the KC135, when assigned a "refuelling" task in the mission editor, to ignore the assigned airspeed and instead fly at ~220 KTAS, and is there a way to change it's speed?

 

*edit* Andyfoot, you are quite incorrect. It is normal to leave the flaps set on "maneuver" for the duration of a mission. There's a reason it's called the "maneuver" setting; it's designed so that if you are maneuvering, and lose airspeed due to that maneuvering, the flaps will automatically deploy to maintain lift. I quite clearly stated that I was making my contact approach with flaps set to "up". So, no. I am not "causing my own problems". The low airspeed of the tanker is causing my problems. If the tanker was flying at 150 KTAS, an airspeed where flaps are REQUIRED to stay airborne, would the root of the problem still be my procedural error in your eyes? Utterly ridiculous.

 

Incidentally, I can still make contact and draw a full tank in one contact. But it takes much more effort than it should

Edited December 31, 2011 by OutOnTheOP
Removed illtemperedness

[OutOnTheOP]

Edited for clarity:

 

Problem: AI-controlled tanker flies too slow.

 

Question 1: Is the tanker scripted to automatically ignore assigned waypoint route speeds set into the mission editor when under "refuel" orders?

 

Question 2: Is it possible to make a tanker fly at 260-280 knots true airspeed when under "refuel" orders? How?

Edited December 31, 2011 by OutOnTheOP

[Jona33]

What's the speed you've set in the orbit menu?

[OutOnTheOP]

First, thank you for taking the time to answer the question at hand.

 

Second, I did not create the mission (I've never really used the ME, hence why I am here asking the question), so... give me a moment and I'll see if I can find out!

[OutOnTheOP]

Apparently there IS no orbit task assigned; it is a linear track (and come to think of it, there was one attempt I made where it got to it's second waypoint and called RTB... so I guess there isn't an orbit?)

 

That said, I found the "add tasking" for "orbit" on the advanced waypoint options, but the only orbit shape offered was for a circle. How do I change it to a racetrack?

[Jona33]

You need a second waypoint after the orbit task to make it a racetrack as this marks where it flys racetrack too before turning to the left for the other leg. If you attach the mission I'll check. Also note that you assign true or ground airspeed (not sure which) in the ME rather than the indicated you fly on.

[OutOnTheOP]

Rog, just figured it out... there were two waypoints, but for some reason it only allowed "circle" on the first; I guess "racetrack" orbit is on the FAR end of the orbit, and consists of that waypoint and the one previous?

 

Yeah, I assumed it was measured in Ground Speed... I just didn't check what that was (KTAS was about 220; KIAS was 180-ish at 20,000 ASL, and 196-ish at 15,000 ASL). All the references I could find for "normal" refuel speeds were in KTAS, though; and indicated 280 KTAS... which is probably close enough, because I don't have very high wind values set.

[Jona33]

Rog, just figured it out... there were two waypoints, but for some reason it only allowed "circle" on the first; I guess "racetrack" orbit is on the FAR end of the orbit, and consists of that waypoint and the one previous?

 

That's weird. It ought to be the other way round.

[OutOnTheOP]

No, you were right, it's the start point... but for some reason the ME wouldn't recognize there was a second waypoint until I added a third (yeah... no clue)

 

Jona, tango mike, problem resolved. Tanker now flying at a solid 270 KTAS; as expected, refueling was a breeze compared to at near-stall-speed.

 

I'd rep you twice if I could.

[sobek]

*edit* Oh, and Andyfoot, you are quite incorrect. It is normal to leave the flaps set on "maneuver" for the duration of a mission.

 

No it certainly is not. The flaps would deploy at speeds where they are not needed.

 

There's a reason it's called the "maneuver" setting; it's designed so that if you are MANEUVERING, and lose airspeed due to that MANEUVERING, the flaps will automatically deploy to maintain lift. But that's ok, I assume you're attempting to troll.

 

Wrong. If you do that, you will absolutely kill your cornering performance. You shouldn't ever get that slow while maneuvering, on a sidenote.

 

You're either an @ss for trolling, or else you simply have truly crap reading comprehension, because I quite clearly stated that I was making my contact approach with flaps set to "up".

 

And you, good sir, would be well advised to go easy on the character sniping with people that are trying to be helpful. ;)

 

Edit: Besides, if you change your post, it would be good practice to actually highlight what you changed or write an edit at the end, because hardly anybody will take the time and read the same post twice just to see what has changed.

Edited December 31, 2011 by sobek

[effte]

Maximum airspeed with flaps extended is 200 KIAS. At FL150, that's about 250 KTAS. If you still have the flap lever in anything but "up" by then, you are in error.

 

The stall speed clean is below 150 KIAS. 220 KTAS at FL150 is around 175 KIAS.

 

Tanker orbit speed for A-10 ops is 255 KIAS, to enable the tanker to slow to A-10 AAR speed of 220 KIAS for the RV.

 

AAR references

http://www.raf.mod.uk/rafcms/mediafiles/4300B099_5056_A318_A8C70417169E52AA.pdf

http://www.raf.mod.uk/rafcms/mediafiles/4300B099_5056_A318_A8C70417169E52AA.pdf

 

Out.

Edited January 1, 2012 by effte
As the name calling was withdrawn, I'm removing the response. Factual and constructive threads are better!

[OutOnTheOP]

Effte and all:

 

For whatever hurt feeling there may be, I apologize. I'm sorry that you feel I was trying to character snipe, but from where I sat, the comments were infuriatingly patronizing, and I honestly believed they were being made with the specific purpose of redirecting blame onto my alleged incompetence for failing to do something I had already said I had already done. I very much did not get the impression that they were said in an attempt to be helpful. I seem to have been incorrect in that impression, and apologize for losing my cool. To clarify why this aggravated me so, my original post had stated that the flaps caused an issue and had to be set into up manually, which may not have been TERRIBLY explicit about my having already resolved that issue ( I said "so you have to manually set flaps up", rather than an explicit "I manually set the flaps to up")... so the first person to mention flaps didn't really get my goat. A bit of "geez, guys, I already covered that" type of annoying, but not infuriating. After I get four nearly identical comments about flaps in a row, and no answers about the questions that were specifically asked in bulletized format, even after I clarified that I have already determined the flaps need to be up, I thought people were just patronizing me. When Andy made a statement that the problems I was having were "caused by me" improperly failing to set flaps to up- after I had already stated I had set the flaps to up, well... then yeah, it looked to me like he was either trying to be deliberately insulting, or didn't actually read the post.

 

Anyhow...

 

1) Stall clean, perhaps. I was not flying a clean aircraft. In fact, I never mentioned the configuration I was flying. Configuration was not germane to the issue at hand.

 

2) Yes, quite aware of the difference between KIAS and KTAS. No, I didn't care enough to pull out a whiz wheel or do the math to give the PRECISE KTAS. Hence "approximately" 220. The precise numbers weren't important to me, the fact that the tanker was flying slower than it should have was.

 

3) The wind comment was in regards to Jona's mention that the ME uses ground speed; I hadn't set wind values very high, so I was telling him that as far as mattered for my purpose, ground speed= KTAS

 

4) yes, I found sources for tanker speeds (to include minimum effective speeds for aileron and pitch control)... but I generally take internet sources with a grain of salt. I was hoping someone might chime in who had firsthand experience.

 

5) If the flaps are never intended to be left in maneuver, then why is it called "maneuver", and why have other aircraft in the past (P-38F springs to mind) used combat flaps to improve turning performance? For that matter, why does the flap switch default to Manuever when you start a mission airborne? The only reason I noticed the ballooning problem was the very first time I tried refueling at that low speed, when I was surprised by the flaps deploying.

Edited December 31, 2011 by OutOnTheOP

[GGTharos]

Correct refueling speed for the A-10 is 220KIAS. Use your math for setting KTAS at different altitudes in the ME.

 

As for flaps, they are used 'as required'. I don't know of any fighter where you leave the flaps down upon take-off, including the ones that have automatically controlled flaperons. Flaps may improve your turn, but they also add drag to the point where it may not be worth it. These are not ww2 fighters - in some cases, a modern fighter outweighs a ww2 bomber. Flaps can ebe easily over-g'd, the retraction mechanism only protects them from being over-sped.

 

Again, use flaps as required. They are not required nor desired by default - you will have to do some self-study on why, but there should be enough hints. Lift vs drag, and desired outcome of the maneuver in terms of rate, speed and other factors are what you should look at.

 

As far as the default goes, that is probably an ommision, nothing more. Check the -1 for basic flight constraints, though it doesn't give you the whole story by far.

Edited December 31, 2011 by GGTharos

[OutOnTheOP]

Thanks. Where can I find the -1? I mean... I know it's a manual, but I come from the Army side of the house, and an artillery background, so... I don't know the rest of the manual nomenclature (and I suspect I won't find much if I google "A-10 -1".... or maybe I will?)

 

*edit* ah, that sounds good; my swag ended up putting the tanker at 231 KIAS... a little faster than it should be, though it still feels a bit nose-high to me. Still, better than the 180 KIAS the mission started at

Edited December 31, 2011 by OutOnTheOP

[GGTharos]

There is an 'A-10 documents'. Thread in this forum - i'd link you to it but posting froma tablet makes things obnoxious for me, so I will have to refer you to the forum search function :)

 

Don't worry about the nose up attitude, you will get used to it. All you need is to be on top of the formation flying and you won't have trouble staying on the boom. If it still apears suspicious to you tough, do post a screen shot.

[Jona33]

There is an 'A-10 documents'. Thread in this forum - i'd link you to it but posting froma tablet makes things obnoxious for me, so I will have to refer you to the forum search function :)

 

Don't worry about the nose up attitude, you will get used to it. All you need is to be on top of the formation flying and you won't have trouble staying on the boom. If it still apears suspicious to you tough, do post a screen shot.

 

http://forums.eagle.ru/showthread.php?t=60293

Not this sticky by any chance GG.

[GGTharos]

That is the one, thanks! :)

[OutOnTheOP]

Nah, not suspicious, just... perceptible; you can visibly see the AOA rise as you decelerate that 20 knots from closure speed to contact speed, and it's a bit disconcerting. The aircraft seems to handle fairly solid at that speed, and I can understand why you wouldn't want to go TOO fast (angular velocity increasing as airspeed increases, causing the same divergence angle to result in increased lateral velocity), so I'm more than happy with 220 indicated.

 

Wait... I think I've seen the post, but the only USAF flight manuals I recall seeing were for the A-10A. Are those the correct ones, or should there be a different one?

[GGTharos]

You are looking for the A-10A-1: http://forums.eagle.ru/showpost.php?p=1015425&postcount=3