F-15 ILS approach profile.

[Ironhand]

 

You'll be able to hold 19AoA at about 141-142kts. I touched down with 115kts, but I could have rounded out the flare a lot more than I did as well, and probably reduced that by 110kts...

Interesting. When I did the math this evening, I came up with an increase of about 1.2 kts for the difference of 500 lbs between the aircraft that you reported. I figured I must have gotten it wrong but perhaps not, given what you did.

Edited November 25, 2014 by Ironhand

[GGTharos]

Hard to tell. Could be the weights are wrong. Could be the FM. Could be the reported speeds/AoA are wrong. Could be he landed on fumes (but doubtful). Could be all of the above :)

[Cali]

Brakes over-heating is not modeled, so there's no actual reason other than 'doing it right' to use aerobraking.

 

Do you know if this is in the works?

[GGTharos]

Hi Cali, I believe it is intended, but I don't know if it is in the works.

[Ironhand]

Hard to tell. Could be the weights are wrong. Could be the FM. Could be the reported speeds/AoA are wrong. Could be he landed on fumes (but doubtful). Could be all of the above :)

That's the problem with incomplete information. Too many variables. Landing on fumes probably wasn't one of them, though. :)

 

 

Rich

[Cali]

Hi Cali, I believe it is intended, but I don't know if it is in the works.

 

Thanks, hopefully it will be implemented soon. Not sure how hard it would be to do.

[Ironhand]

Hard to tell. Could be the weights are wrong. Could be the FM. Could be the reported speeds/AoA are wrong.

So I spent about an hour this morning making circuits and discovered 2 things: 1) I suck and 2) after an hour of flying, I suck slightly less. :) I also discovered that with the right altitude and starting point, I could very comfortably hold a consistent 140 knots down to the threshold at 19 uAoA. It never felt like I was riding the edge. This was starting with 30% fuel on a clean aircraft and using a 4* glide slope which is a bit steep. The problem was that I'm so inconsistent in my pattern that I have difficulty hitting the groove with any sort of consistency.

 

Part of my problem is that I'm trying to do too much with too little pit experience. Holbeach had a video elsewhere showing circuits at RAF Lakenheath. I went to an external view of my flight and realized that my climbing turn looked very much like what was in the video. But I was leveling out at about 2500 ft, not 1500. As the hour went on, though, I was getting a lot closer to the right altitude and airspeed at the top. Since I was trying to do that at the same time, I wasn't as focussed as I should be. But..Damn! This is fun!

 

BTW, what's the critical AoA of the F-15's wing?

[GGTharos]

No worries, you'll get the hang of it ... just requires a bit of practice :) For just this particular set of numbers you can shoot straight-ins.

I suggest before you nail the pull-up, nail the overhead - ie. come in at 300-350kts down the runway at 1500' AGL, then do a 3g break into the reciprocal. Maintain altitude, roll out at 220kts. Make sure you're 6000lbs of fuel or less, otherwise execute a straight-in.

 

I don't know what the critical AoA is (it's somewhere around 40-some units), but stability is significantly decreased at or past 30 units, especially if you have any asymmetries. The rule is to go around if you hit 30. Don't try to save it, don't try to decide if it's still good and you can make it, just go around.

Edited November 25, 2014 by GGTharos

[Ironhand]

...

 

I don't know what the critical AoA is (it's somewhere around 40-some units), but stability is significantly decreased at or past 30 units, especially if you have any asymmetries. The rule is to go around if you hit 30...

Good to know. Thanks.

 

...

I suggest before you nail the pull-up, nail the overhead...

 

:) My problem is that most of my free time happens early in the AM before I've consumed my 3rd cup of coffee. I'm a bit more focussed after that.

[GGTharos]

I just had to think about it again though ... he said he shot an ILS approach, so there's really not much of a choice but to be on the 3deg glide-path, unless he's doing it differently for some unknown (to me) reason.

[Holbeach]

How are we getting on with the 110 kt touch down, bearing in mind he had enough fuel on board to go and do afterburner high speed handling trials after the ILS approach, but the landing was done after bingo called.

[GGTharos]

But you don't know what bingo is. Bingo can be set right on the fuel gauge. The only possible guess as to the fuel loading comes from the described speed and AoA, and they seem on the very edge of plausibility - but this also assumes basic weights of those aircraft (A,B) have not changed since the 70's (my -1 is late 80's).

 

Also, what are high speed landings? What did he need afterburner for exactly? And if he did have the fuel for it, then landing as he described becomes implausible.

 

At this point it becomes anyone's guess whether it's instrument error, pilot calling it 'yeah looks like 19 units', the FM being off, the available numbers for aircraft weights being incorrect, etc.

 

And this is exactly why the -1 parameters are used, which are collected and averaged over many test flights, not some guy's single flight.

Edited November 25, 2014 by GGTharos

[Ironhand]

I just had to think about it again though ... he said he shot an ILS approach, so there's really not much of a choice but to be on the 3deg glide-path, unless he's doing it differently for some unknown (to me) reason.

I'd forgotten that little tidbit. He did say that. I know you cited numbers that indicated a 500 lb differential between the -B and -C models but I wonder if it's bigger than that. We'll never know what the exact reasons for the differences are between that passage and the sim experience. Even if it's comparing apples to apples, you're comparing Cortlands to McIntoshes--or whatever. :) So not exactly the same.

 

EDIT:

...What did he need afterburner for exactly? And if he did have the fuel for it, then landing as he described becomes implausible...

Afterburner happened later as part of a high speed test run. So, come to think of it, he had enough fuel to fly, almost land, run at high speed in afterburner through Mach 1 in the test corridor, bingo, and RTB.

 

:END EDIT

 

Regardless, I'm having fun in the cockpit.

Edited November 25, 2014 by Ironhand

[GGTharos]

I re-read the entire approach. No way he shot it at 19 AoA. He may have held it for a little while (he did a 15nm straight-in), but there's no way he was on glide-slope, shooting 19 units all the way in at 140kts. The language is there too: 'About 140kts', isn't 'dead on' 140kts. The very specific mention of buffet at 20.5 units is like something out of a text-book, following 'about' 140kts (ie. 'as I recall ... ' ). The 110kt is not part of this approach, it's done later and achievable in-game with the right technique.

 

He had enough fuel to do more stuff, so this wasn't a landing at minimums or anywhere near that - in other words, matching gross weight in the sim should not be a problem.

 

I'd be inclined to think that the report is quite simply not a scientific one and that's all there is to it. Some parts are accurate, some are not.

 

And thus, once more, this is why the -1 is the authoritative document on this aircraft, and not anecdotes.

 

I'll add this: You can fly all the streak-eagle profiles with the in-game F-15C and match them very, very closely. But you have to fly the profile exactly right, right down to having no oscillations about your intended flight path.

Edited November 25, 2014 by GGTharos

[Holbeach]

 

Also, what are high speed landings? What did he need afterburner for exactly? And if he did have the fuel for it, then landing as he described becomes implausible.

 

At this point it becomes anyone's guess whether it's instrument error, pilot calling it 'yeah looks like 19 units', the FM being off, the available numbers for aircraft weights being incorrect, etc.

 

A.

 

High speed handling, not landings.

 

The pilot was very specific about the AoA. 19u and if it gets to 20.5u then increase by rpm by 1% to get it back to 19u.

 

Any pilot entrusted with the F-15 test plane, will be precise.

[GGTharos]

This was a trainer, not a test aircraft. The TF-15 is the F-15B, which is a production aircraft. It should fly like the -1 says it should fly.

 

There's only the semblance of precision: You're not going to be able to tell 20.5 units from 20 or 21 given the available instruments, and he uses the word 'about' regarding his speed, which makes sense. It is not possible to fly the glide-path at 140kts AND 19 units AND GW more than 28000lbs which he must be above. It is a physical impossibility, and you don't need to rely on the in-game FM (nor should you rely on it) to tell you so. The -1 is all you need.

 

He also doesn't say 'increase 1% RPM to get back to 19u', he just says you can use this to get out of the buffet.

 

The only possible things that come to mind that could make up the difference: Flying a non-production aircraft and maybe, MAYBE flying a very non-standard day, but the latter seems fishy.

 

Edit: Just read he extended the airbrake. This might make a huge difference - or not - because the airbrake puts your descent through the floor. So I'll re-try it with the airbrake out.

Edited November 25, 2014 by GGTharos

[Holbeach]

This was a trainer, not a test aircraft. The TF-15 is the F-15B, which is a production aircraft. It should fly like the -1 says it should fly.

 

 

 

 

This was not a trainer.

 

It was 1 of 2, category 1, test aircraft at Edwards AFB, used as a development

test bed, both of which went on to become concept demonstrators for the F-15E.

 

The man in the back seat was a MD test pilot.

[GGTharos]

The TF-15A is the F-15B. There are hints that this one is non-standard (possible hints of radar controls in both cockpits), but it shouldn't really fly different.

[GGTharos]

Same deal with the air brake. Can't do 140kts with 19 units on a proper glide-path.

 

Edit: Approach speed chart from -1 included in this post.

Edited November 25, 2014 by GGTharos