Landing without hydraulics

[Steinsch]

Hi there,

 

I'd like to know if anyone could share their experience about landing the F-15 without hydraulics-dependent systems (air and wheel brakes mainly).

 

The bird bleeds speed very slowly under 200 knots and it's extremely difficult to flare, as nosing up will actually increase lift and altitude will be a gained again.

The difficulty can be compounded when the ACS has been damaged as well.

 

Landing at Batumi in these conditions is a real challenge. Is there any proper available procedure for the F-15 as modeled in DCS?

 

Thanks!

 

Steinsch

[GGTharos]

If your hydraulics are out you should eject.

 

It isn't completely modeled in game, but no hydraulics = no control. With only 210kts to spool the engines, you should be getting unwanted control transients.

[TAW_Blaze]

Set up a decently long final, not too long, stay around 19 uAoA, aimed at the start of the runway this will usually give you an easy landing without having to flare really hard. If you have to flare very hard you failed your approach, for whatever reason it is. Most commonly being lazy is the reason :)

 

You can lower flaps without hydraulics so it shouldn't be much of a problem, aero brake after touchdown (careful not to liftoff again). If you have no brakes you might not be able to stop on a shorter runway like Novo or Gele. Batumi isn't much longer but should be fine.

[Steinsch]

Thanks guys.

 

So I understand that in real life, ejection is recommended, but in the game it's still possible.

I'll practice with a 19 AOA and see how it goes.

 

Thanks again.

[GGTharos]

In the game it shouldn't be possible but the damage model isn't quite complete.

 

In RL, if you lose one hydraulic system you'll be laughing. If you use both sides, you can't do anything at all. You can't move the control surfaces.

 

Recall the Israeli F-15 that lost a wing: He most definitely lost one of his hydraulic systems too :)

 

If you're out of fuel and engines are wind-milling, the minimum speed to provide controllability is (IIRC) 210kts, which you can't really land with.

 

You can run the APU to provide enough RPMs on at least one engine to give you controllability for such a landing, but it has never been attempted because it's dangerous.

 

In other words: If you're out of fuel, you might be able to operate the hydraulics but at reduced and possibly unpredictable capability. In RL, the USAF very strongly recommends that you leave the plane in this situation - by very strongly I mean it's probably your emergency procedure, so you'll be ejecting.

 

If you have LOST hydraulics, you should not be able to move a single control surface, period. EJECT EJECT EJECT!

 

In other words, you probably didn't really lose hydraulics - maybe you lost the CAS :)

 

The whole airbrake/wheelbrake inop thing is not correct IMHO.

Edited June 26, 2015 by GGTharos

[Exorcet]

I suppose in the situation where the plane is controllable, arrestor cables and nets may come into play(?), though they aren't modeled.

[Steinsch]

In the game it shouldn't be possible but the damage model isn't quite complete.

 

In RL, if you lose one hydraulic system you'll be laughing. If you use both sides, you can't do anything at all. You can't move the control surfaces.

 

.

 

Thanks for the additional info.

 

I've stumbled upon this page:

 

http://www.f15sim.com/operation/f15_hydraulic_system.html

 

It seems the hydraulic system of the F-15 is quite resilient thanks to redundant subsystems. Is it possible that a "Hydraulics failure" in the game could be a partial failure only, hence explaining while I still have control but brakes have ceased functioning?

Edited June 27, 2015 by Steinsch

[Steinsch]

Set up a decently long final, not too long, stay around 19 uAoA, aimed at the start of the runway this will usually give you an easy landing without having to flare really hard. If you have to flare very hard you failed your approach, for whatever reason it is. Most commonly being lazy is the reason :)

 

You can lower flaps without hydraulics so it shouldn't be much of a problem, aero brake after touchdown (careful not to liftoff again). If you have no brakes you might not be able to stop on a shorter runway like Novo or Gele. Batumi isn't much longer but should be fine.

 

Could you please confirm if emptying my fuel tank to be lighter would help in reducing the landing distance?

[TAW_Blaze]

Could you please confirm if emptying my fuel tank to be lighter would help in reducing the landing distance?

 

It probably would, but having only internal fuel left you shouldn't have any problems landing. I actually unbinded fuel dump and left it without a command because every now and then you just happen to missclick it and then it's not very funny. I don't recall using fuel dump ever on purpose in DCS. If you still have external tanks obviously drop those.

[GGTharos]

I don't believe that you could realistically lose those if you had any of the hydraulic systems operating. Plus they are fed from the emergency system as well.

 

It seems the hydraulic system of the F-15 is quite resilient thanks to redundant subsystems. Is it possible that a "Hydraulics failure" in the game could be a partial failure only, hence explaining while I still have control but brakes have ceased functioning?

[esb77]

It probably would' date=' but having only internal fuel left you shouldn't have any problems landing. I actually unbinded fuel dump and left it without a command because every now and then you just happen to missclick it and then it's not very funny. I don't recall using fuel dump ever on purpose in DCS. If you still have external tanks obviously drop those.[/quote']

 

I've used fuel dump when doing emergency landings in very badly damaged planes, especially for gear up landings.

 

If you get it just right and run the tanks empty just about when you touch down, it prevents the plane exploding due to fire, as the fire will extinguish something like 20 seconds after the engines flame out due to lack of fuel.

 

You can do this to buy time in a burning plane if shutting down engines and activating fire suppression systems doesn't do the trick, though I wouldn't recommend it at more than the default bingo fuel, as it's a race between heat accumulation and dumping fuel, and if you have a lot of fuel you'll get to a tank explosion before you get to an empty tank.

 

Mind you, I don't think this is a particularly realistic approach to how aircraft fires work, but it works in game.

[Potalien]

By coincidence I managed to do a no hydraulic landing (no flaps, airbrakes or wheel brakes) the other night. Basically it involved holding the nose up as high as possible without having the engines scrape for over half the runway. I had no payload at the time and came in with very low fuel after my second attempt so that made it easier though. I'll record the trk file and post a link to it in the next few days.

 

My approach was:

1 - Land at the very beginning of the runway at between 130 - 150

2 - Body brake at Max Alpha I could get away with, I can't remember the exact figure but I'm pretty sure it was over 15°

3 - Keep nose wheel off the ground until I was under a 100 at minimum, I'm pretty sure I dropped mine between 60 - 90

4 - Once under 60 I used gentle swerving to each side of the runway to bleed off speed

 

It worked but I'm not sure how my luck would run if I tried it again.

Edited July 16, 2015 by Potalien

[GGTharos]

My approach was:

1 - Land at the very beginning of the runway at between 130 - 150

 

Just approach with and land using normal AoA and flare parameters.

 

2 - Body brake at Max Alpha I could get away with, I can't remember the exact figure but I'm pretty sure it was over 15°

 

It's 13. Under 13, aerobraking is ineffective, over 15, you're banging the tail on the ground and there's absolutely no point to it.

 

3 - Keep nose wheel off the ground until I was under a 100 at minimum, I'm pretty sure I dropped mine between 60 - 90

 

That's about normal.

 

4 - Once under 60 I used gentle swerving to each side of the runway to bleed off speed

 

It worked but I'm not sure how my luck would run if I tried it again.

 

I don't know about bleeding speed, you'll certainly travel a slightly longer distance by doing so though.

[Steinsch]

My trk files don't work (it's particularly bad with beta 1.5), so I made a video of a landing without hydraulics:

 

 

Probably not the real life procedure as GGTharos mentioned, but it works in the sim.