AAR violent pitch up after starting refuelling

[grim_reaper68]

Hi

I'm actually training AAR with the F1, I noticed that it pitches up violently atfter starting refuelling. I've made a mission where there is only 850 liters of fuel, so the tanks are almost all empty. I checked the fuel panel after this pitch up and noticed that the first tanks that are filled are the 5, so the aft tank. I could figure that it's like IRL, but hard to manage for an AAR beginner like me. 

[fausete]

Hi, can you include a TRK please (in the Caucasus and SP). Take into account you might be flying into the wake of the tanker.

[gulredrel]

Also what's the tanker's and your own speed and AoA? Maybe you are on the edge of slat extension?

[grim_reaper68]

Tanker alt 15000ft, speed 340kts to avoid converter overheat. No slats. No wake activated. I post the trak ASAP.

 

and the trak. As said I'm a total AAR newbie, so maybe it's me. 

DCS Mirage F1 AAR.trk

Edited January 9 by grim_reaper68

[SabreDancer]

It looks from the video to be pilot-induced oscillation. Getting out of position in comparison to the tanker, overcorrecting steering in an attempt to go back to center, then noticing and overcorrecting the other direction, etc. Unfortunately the track is broken from my perspective, and seems to show the aircraft flying below and past the tanker.

Edited January 10 by SabreDancer

[gulredrel]

I also think just PIO. You are falling slighly behind, adding power, than closing in too fast and reducing power far below the level it was before increasing power.

Power changes are accompanied with pitch changes. I think, you just need to anticipate the changes in pitch when changing power to not overcorrect. Constantly tiny power changes are better than large bursts.

[grim_reaper68]

Ok, I will continue practicing. Compared to other aircrafts like M2000 and F18, the F1 is a real challenge. But every attempt is better, so hopefullly, I will manage to make a good AAR soon. 

Did you try to make an AAR with less than 800 liters on your side, so that all tank lights are on? I can figure that your level is far up compared to mine, but maybe you can notice this tendency to pitch up. In my opinion, if the rear aft tank will be filled first, it's normal that there is a need to push on the stick to compensate the add of weight at the back of the aircraft. That would be a proof of the great work from Aerges of the reallistic flight model of the F1.

Thanks for your advice. 

 

[gulredrel]

18 and 2000 are full FBW, so there is much more automation involved.

I was fairly successful in the Tomcat lately, haven't refueled F1 for too long. With everything, it's a matter of practice and getting used to the changes needed to compensate for the increasing fuel weight.

[grim_reaper68]

I would say the F1 is really an old school aircraft. In France the pilots says "qui se pilote avec les fesses" , litteraly translated "which is controlled with the buttocks" . I'm sure you understand the meaning.

I tried an AAR with the F14, 340kts, the aircraft is hard to fly, like there where wake turbulences, but they aren't activated in my training mission. I tried one time with. I killed the tanked so I was angry .

I also found a way to cheat AAR with the F18, I forgot to shut the AP off, it was incredebely easy, very stable. I noticed it as I was flying aways from the tanker as the alarm cames up.

[SabreDancer]

As one more possible aid, do you add curves to your joystick? It's incredibly helpful for fine aircraft control in situations like air to air refueling.

[grim_reaper68]

Hi, yes I have curves. As said I'm a newbie on AAR, but now with training, I managed to predict the pitch up, and can almost make a complete fuel transfer in one time. I will try to make a AAr with more than the minimum fuel to see if the pitch up appears. As mentionned with all tank lights on, the first who where be filled are the rear aft tanks (5 on the tank panel), so the center of gravity of the F1 goes back. I'm surprised to see the realism level of the F1, which take in account that sort of parameter in the flight model. Did you try an AAR with 20% of fuel? I would be glad to see if it's only my impression or if it's really the FM of the F1.

[gulredrel]

3 hours ago, grim_reaper68 said:

can almost make a complete fuel transfer in one time

Currently I'm in the F-14 and managed to get around 11000 lbs of fuel without disconnect in between. Need to try my luck with the F1EE.

[gulredrel]

Just a quick update. Did two AAR with the F1EE. Tanker was going 300 kts IAS at 15000 ft.

For me it worked best when starting with a good amount of down trim, so I had to constantly pull on the stick to keep same altitude. Once connected regulating the throttle and relaxing the pressure to not gain any altitude when the CG shifts a bit and also the attitude wants to change with the change in power. It's just a matter of practice.

The down trim and constant slightly pull is especially helpful, if your stick has some wiggle in center position. So you the necessary corrections do not move through possible dead zone which is maybe applied (hope I've explained that right and you know what I mean).

Haven't tried with external tanks yet or with an KC-130 going slower than 300 kts IAS, but this will be next level.

[grim_reaper68]

External tanks wouldn't make any noticeable difference on the attitude, as they're close to the CG. I know I'm crazy as newbie on AAR to try "heavy loaded" aircrafts, but in my mind if I'm able to make it with clean or heavy loaded aircraft, it would be easy to understand how they react with or without load. I even made an AAR on the IL78, single and then with an SU33 (I would like to make a joint flight with the SU27, like the pilots from the Normandie-Niemen, but as they aren't AAR capable...) , in the mind to practice AAR on the right side of the tanker. I was surprised to see that the lights of the IL78 are very visible compared to the KC135, and almost indicates if you're flying too fast or too slow. Strange thing too, hearing my "french" pilot speaking russian. As I'm gaining experience on AAR, I'm challenging myself . I even made a try on the IL78 with 2 SU33 refuelling, he tells me to wait... Why having 3 drogues if you can't use them 

For making AAR with the KC130, good luck, as far as if you're flying too slow you would have both inverter failing (tested on KC 135 flying at 260 kts)