Landing…F-16 feels really unstable...
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I am not sure if this is a feature or not, but on approach to land the F-16 felt really sluggish, and i had a hard time keeping it aligned with the runway. As soon as i dropped the landing gear, it smoothed right out. Was my speed just too slow, or is some other forces being simulated? This was training TE 2, but i landed it as well. Stuck it too!
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You would need to provide a little more detail than that to be able to work out where the problem lies. Generally speaking though, at approach airspeeds the aircraft will have less G available but should otherwise have a similar response to inputs. After you lower the gear, the FLCS gains switch over to takeoff/landing gains, which will transition from G command to pitch command per stick force.
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Common 11° approach technique should feel sluggish. It means you are on the backside of the power curve. 13° approach technique is even farther. You should find that pulling up to try to fix sinking mostly results in more AOA, more drag, and less speed. Speed is gained by reducing AOA. Throttle at a constant attitude adjusts the flight path angle.
Landing gear down changes the FLCS program, extends the flaps, and has a small lift component. Gear is normally extended approaching the glide slope level from below at ~250 knots for straight in or at the “perch” for the tactical overhead pattern, usually ~2000’ above the runway elevation.
Common mistake for lateral alignment problems is lack of appropriate maneuver to realign and compensate for any crosswind aggressively and early. For example if you are 2000’ right of approach alignment, place FPM at least 2000’ left of landing threshold to achieve centering at half the distance to go. Look for a perfectly vertical “capital I” runway picture as early as possible and don’t accept any noticeable misalignment or drift due to crosswind.
Speed should produce 7-9° AOA initially slowing to 10-11° smoothly as early as possible. When all significant errors have been eliminated and the runway is less than a minute away manage throttle to keep 11° top of AOA bracket through ground turbulence. FPM will wobble at low level, changing pitch will just produce excess drag and problems. Watch for average movement and identify if more throttle is needed. FPM should be placed at very beginning of concrete surface until the flare.
At 30-50’ height pull back stick to decrease descent while reducing throttle to idle. AOA should reach 13° middle staple (no more than 15° bottom staple) as main wheels touch down. If 13° is flown instead of 11° approach then decrease in descent in flare is done entirely by adding throttle briefly with no pitch change.
In crosswind, point nose into the wind to make wings-level ground track aligned with runway. Do not use rudder during final approach, flare, or touchdown. Strive to touch down both MLG together and allow airplane to pivot naturally after touchdown to align with runway. A slightly harder touchdown is acceptable with crosswind.
Keep green circle on-speed AOA indication illuminated with pitch after touchdown. Less than “doughnut” speed is very ineffective at slowing the airplane. Avoid exceeding 15° AOA as the airplane may scrape the runway. At ~90-100KT lower the NLG as gently as practical, open the speed brakes all the way and brake as needed. Aft stick can tilt the tailerons up adding drag and putting more weight on wheels for braking.
At a safe speed engage NWS and taxi off the runway at 10KT.
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You might get thrown around a bit due to low level wind shear when you’re on final but also, control surfaces are less efficient when you’re flying at slower speeds - look up “back of the power curve” and the Wikipedia article on “slow flight”.
Not sure why the gear would have sorted it out though - maybe it was just low level wind shear or gusting winds?
Cheers,
Del
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Control suface efficiency is irrelevant - the control surfaces are positioned by the FLCS based on stick input to achieve a certain effect on nose position which varies based on the stick force, and is constant with changes in airspeed.
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Speedbreaks are usually open all the way out during approach,
if not, open them as you touch down, to help aerobreaking as much as you can. no point in opening them at 90 knots or so. -
Control suface efficiency is irrelevant - the control surfaces are positioned by the FLCS based on stick input to achieve a certain effect on nose position which varies based on the stick force, and is constant with changes in airspeed.
Was going from my experience in a 152, didn’t think about F16 differences. Thanks for the info.
Although thinking about it, OP is asking about sluggish controls, not resultant behaviour so wouldnt that mean that slow airflow over the control surfaces would have an effect? Not sure how the FLCS could compensate for that slow airflow? Even an F16 flies differently at very low speeds.
Cheers,
Del
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It compensates for decreased airflow over the control surface by increasing the deflection. Same way a wing deals with decreased airflow, by increasing angle of attack.
According to the dash one, the F-16 handles without significant difference across its speed range and that typical handling cues which normally indicate increased or decreased are not present.
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It compensates for decreased airflow over the control surface by increasing the deflection. Same way a wing deals with decreased airflow, by increasing angle of attack.
According to the dash one, the F-16 handles without significant difference across its speed range and that typical handling cues which normally indicate increased or decreased are not present.
Man, I need to re-read the Dash 1 [emoji1]
Thanks for the info!
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Do note that there is a minimum airspeed, below which the control surfaces cannot generate nose movement anyway, regardless of the deflection used. Seeing as that low airspeed starts running into higher angles of attack than the FLCS limiters allow, either a nose down movement is commanded by the alpha limiter which allows airspeed to increase again, or it is insufficient and you end up with a departue that could progress to a deep stall (if angle of attack stabilises at 60 degrees).
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Thanks guys!
@Frederf I really appreciate you providing that info. I have a lot of homework.
@Blu3wolf I am not sure if sluggish best describes what i experienced, but some of this stuff is hard to put into words. On TE Training 02 everything felt normal, and the F-16 flew straight. When i started dropping altitude and began lining up my approach, the entire behavior on the plane changed. The nose seemed to be bouncing all over the place, and i needed almost full left stick to keep it even remotely level. The tower instructed 220 kt, but i was fighting it so hard i am not sure if i was 250 or 200. I drop the gear and it is completely normal and smooth again. I did not use the speed breaks to slow down.
I am going to do it a bunch more times, so i will report back once i have tried it using the procedure Frederf kindly provided.
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I am wondering if it might have been a fuel imbalance issue? I remember seeing a pretty decent red area on the fuel gauge, but didn’t know how to fix it (I do now). Since this was the second TE (navigation), is this relevant to the a/c used, which I think is the Block 15?
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It could also be landing gear gain. FLCS changes gains when landing gear is deployed. Check this post (and the whole thread if you can disregard the silliness). https://www.benchmarksims.org/forum/showthread.php?6987-Slow-Flight-Flight-model-question&p=84638&viewfull=1#post84638
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Thanks guys!
@Frederf I really appreciate you providing that info. I have a lot of homework.
@Blu3wolf I am not sure if sluggish best describes what i experienced, but some of this stuff is hard to put into words. On TE Training 02 everything felt normal, and the F-16 flew straight. When i started dropping altitude and began lining up my approach, the entire behavior on the plane changed. The nose seemed to be bouncing all over the place, and i needed almost full left stick to keep it even remotely level. The tower instructed 220 kt, but i was fighting it so hard i am not sure if i was 250 or 200. I drop the gear and it is completely normal and smooth again. I did not use the speed breaks to slow down.
I am going to do it a bunch more times, so i will report back once i have tried it using the procedure Frederf kindly provided.
what are your weather settings ?
are you flying over water ? city ? fields ?
i put my bet on mechanical turbulence, though it does not require Full stick ….actually even in haevy turbulences, the best thing is to do nothing…
A video would help
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It could also be landing gear gain. FLCS changes gains when landing gear is deployed. Check this post (and the whole thread if you can disregard the silliness). https://www.benchmarksims.org/forum/showthread.php?6987-Slow-Flight-Flight-model-question&p=84638&viewfull=1#post84638
nope he said after Gear down, problem stops
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what are your weather settings ?
are you flying over water ? city ? fields ?
i put my bet on mechanical turbulence, though it does not require Full stick ….actually even in haevy turbulences, the best thing is to do nothing…
A video would help
It was the Training TE (#2 on navigation). I believe it started happening as I turned into the final steer point, which I believe was over water.
Guys, I really appreciate all the help. Just keep in mind that I am on Training Mission #2, so I probably have a ton of other things going on that could be a factor. I don’t know what I don’t know, but I am really enjoying the journey!
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Speedbreaks are usually open all the way out during approach,
if not, open them as you touch down, to help aerobreaking as much as you can. no point in opening them at 90 knots or so.Actually full speedbrakes are 60 degrees open. When landing gear switch is moved to the Down position, speedbrakes automatically retract to 43 degrees unless you override that.
You should not do this until 3-pt braking, because in the 2-pt aerodynamic phase, speedbrakes of 43 degrees or greater can contact the runway if you exceed 15 degrees pitch.
To summarize: only fully open your speedbrakes (beyond 43 degrees) once all 3 wheels are on the ground, and not before then.
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Sadly in BMS the speedbrakes have no collision box, and opening them fully at 13 degrees aerobraking will not cause a scrape (it should).
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Sadly in BMS the speedbrakes have no collision box, and opening them fully at 13 degrees aerobraking will not cause a scrape (it should).
Try scraping the hook.
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Sadly in BMS the speedbrakes have no collision box, and opening them fully at 13 degrees aerobraking will not cause a scrape (it should).
Try scraping the hook.