Braking method on landing.

[98abaile]

I've been practising landings in the F-15 but I always find I run out of runway if I don't touchdown (at about 170kts) near enough right on the threshold and aerobrake at >10 degree all the way down to about 80kts, which is how I thought it was supposed to be done.

 

I've just watched a formation landing video by simis g however and noticed he did very little aerobraking. I can only assume he is using his toe brakes to do it.

 

My questions are:

At what speed can you put on the brakes?

How should I be aerobraking/braking?

Can you do both at the same time?

[ruddy122]

98abaile,

 

Here are two tracks showing how I land at Kutaisi (2500 m/8200 ft). It's not my best landing but I can walk away from them.

 

The key is landing in the first 500 ft of the runway and aerobrake properly.

 

In the F-15 I can put on the brakes at or below 100 kts (holding it for a couple seconds and release)

 

Below 50 kts you can hold the brake pressure til it stops (i.e. hold the brake button)

 

Aerobraking, I put the " W " symbol at 10-11 Nose up and hold it there till below 100 kts and then I lower the nose wheel.

 

Do not try to aerobrake and brake at the same time because you will force the nose wheel down pretty hard.

 

Hope this helps.

Batumi X-Country 01.trk

Batumi X-Country 02.trk

[CHRISXTR3M3]

Why not try to put your nose gear into the ground when coming in too hot and you don't want to abort? Works perfect for me. Just pitch nose down after wheels touch down, activate air brake and wheel brake too.

[blkspade]

I'm surprised that I might beat GG in here. Basically you should be landing according AOA units. The speed is always going to vary due to other factors (mainly weight) but going by AOA corrects for this. Put your velocity vector where you'd ideally like to touchdown and adjust power to maintain 21 units AOA. Any more than that and you'll be descending short of that point, any less and you're likely over speed. A little flare over the threshold and you should touchdown smoothly.

 

As for aero-braking a similar rule applies that you have to hold a minimum of 23 unit AOA for it to be effective, and no more than 25 (to not drag the tail). With the engine idle, the nose should fall on its own once the speed is low enough (maybe with air-brake) without using toe brakes. You're not supposed to use toe brakes without all 3 wheels down. Even if its not currently modeled, it might someday result in damage to the nose gear in doing so.

 

If you can do this perfectly at Gelendzhik, and not run out of runway, then you'll be good anywhere.

[98abaile]

I've been getting better.

It seems the video I watched was quite old, so I assume it was before the PFM. I've been watching some of the more recent ralfidude videos and it doesn't seem much different to what I'm doing (although his are noticeably smoother).

 

I've been putting the threshold at about 3 degree on the ladder and then putting the VVI on it and landing (is that too steep on touchdown?), I'm usually not paying attention to the AOA at that point and instead focusing on trying to raise the nose without taking off again and also not letting my nose go above 15 degrees.

[GGTharos]

I've been getting better.

It seems the video I watched was quite old, so I assume it was before the PFM. I've been watching some of the more recent ralfidude videos and it doesn't seem much different to what I'm doing (although his are noticeably smoother).

 

What gave you the idea that he knows how to do it right? (That's not to say he doesn't, I'm just questioning your judgement :) )

 

I've been putting the threshold at about 3 degree on the ladder and then putting the VVI on it and landing (is that too steep on touchdown?), I'm usually not paying attention to the AOA at that point and instead focusing on trying to raise the nose without taking off again and also not letting my nose go above 15 degrees.

 

The normal landing approach will have you on a 2.5-3 deg glideslope, so if your FPI is at -3 degrees and it's sitting on the edge of the runway you're alright.

 

You "stop paying attention" to AoA a little before you expect to flare, but there's a reason why I put that in quotes. blkspade described the correct parameters for your landing approach. This is the standard landing technique.

 

A recap:

 

Approach with 21AoA and 2.5-3 deg glideslope. Use THROTTLE to mainain correct glide-slope once established (corrolary: be trimmed to fly this in hands off :D ). Fan the airbrake if you need it, do NOT leave it out.

Flare smoothly to 13-15deg (don't overdo it, you don't want to baloon or stall your descent too high) when the runway corners hit your HuD frame or when you feel ground-rush.

ABORT if your parameters are wrong and you feel like you have to fight to fix it. Just don't do it, go around if you're out of parameters at half a mile.

 

If in a formation landing, make sure your FPI does not reach the horizon - in formation landings you want a half degree under or less, but in essence the idea is to 'put it down a bit harder' so that you and your wingman land together.

 

There are other landing techniques for minimum-ground run (2deg glideslope, 23 AoA approach, nose down after touch-down, air-brake and max brakes on after touchdown, NOT BEFORE).

 

You may have noticed that I don't like the air-brake to be out when touching down. This is because that device increases your sink rate and makes your landing approach less stable.