Gear stuck UP?

Couldn't put my gear down the other night. I don't really know why this happened, although I think I might have oversped my gear before I put it up on takeoff.

You probably left the gear in the up position during flight, which makes you lose air from the compressed air tanks continuously. You have to make sure to put gear lever in neutral after takeoff to avoid this..

You also have the emergency gear release

IIRC the gear is hydraulic, it's the wheel brakes and chute which are running off the pneumatic system. Wheels should still come down. Some sort of system damage maybe?

Yes, gear extension and retraction is in normal mode hydraulic. Only the emergency gear extension is done with compressed air of the emergency air reservoir.

Every time I forget to put my gear into neutral after retraction, it will run out of air. When it runs out of air, gear will no longer come down with the gear lever. I was under the impression the system was pneumatic. If not, what causes the gear to stop working when your air gauge reads empty?

An old but effective answer to the question of how the landing gear works: RTFM.

From the DCS MiG-21bis manual:

Gears handle

An important feature of DCS MiG-21BIS is the gears handle: it has

a locker that prevents retracting the gears during ground

operations. Whenever you start your mission, this locker (LV43)

will be in the locked position, preventing you from retracting the

gears. Before you retract your gears, you need to unlock it by

placing it in upper position. On the other hand, there is no

restriction when moving the gears handle to neutral or down

(extract gears) position. Neutral position is important: when you

retract your gears, compressed air is used to brake the tyres and

prevent them from rotating. Once you retract your gears, place

the handle in neutral position to prevent further consumption of

compressed air. If you forget to do this, you may waste all of your compressed air during flight, so

when you land, you won’t be able to use your brakes and drag chute, since these two important

systems consume compressed air as an energy source.

That wasn't what he was asking, he's asking why the wheels themselves aren't coming down. The emergency system is pneumatic but the normal system is not, it's hydraulic.

All I can think of is that you've somehow damaged the undercarriage in such a way as to prevent the doors opening again, or for some unholy reason the hydraulic system is running at such low pressure it won't drop the gear - but then you'd have flight control problems, too.

I don't remember if there's a shutoff valve that prevents any hydraulic oil running to the gear mechanism, as I've never had to isolate it, but that's all I can really think of outside of damage or some really weird bug.

An old but effective answer to the question of how the landing gear works: RTFM.

 

From the DCS MiG-21bis manual:

Congratulations, you completely missed the topic.

But without further input of the OP, we cannot really help either.

Congratulations, you completely missed the topic.

 

But without further input of the OP, we cannot really help either.

I think he was responding to me. I thought the gear was pneumatically actuated. But apparently I “misremembered” about not being able to deploy gear without air. It was brakes, not gear.

As far as the original poster, I cant think of anything else that makes sense unless some sort of battle damage or complete loss of hyd pressure

I had read every post, so no one needs to feel like they in any way contributed to my errant post. But let me make up for my obknoxious off-topic comment by saying I experienced the exact same problem the other night. I left my gear lever up until I went to land. My air was out. My gear didn't extend. I presumed that the landing gear depended on air pressure to be actuated, since that is the only thing I noticed being wrong (i.e. touching the brake lever got zero response from the pressure needles).

So, I just ran a test flight. I intentionally left the lever up and drained down air pressure to zero. Again, I verified I was out of air by touching the brake lever. After doing so, I was able to lower/raise the landing gear at will 20 times. I did not experience the failure I had the other day. It seemed like the landing gear was taking a little longer to deploy after so many lower/raise cycles, but that is probably because I the hydraulics were being pushed too hard or I was just imagining the slightly slower response.

So, back to the original problem: why did the gear not deploy despite being independent of the air, not just for the original poster, but in my experience the other night as well? Could it be the hydraulic system is also programmed intentionally or accidently to bleed pressure if the lever is up too long after takeoff? I didn't do anything to damage my systems the other night, beyond leaving the lever up. So, either:

1) The MiG-21bis is programmed to have random landing gear failures, but that is highly unlikely because I have never had a failure before until the other night.

2) The hydraulic system is programmed to eventually fail if the landing gear lever isn't returned to the neutral position.

3) There is an intermittent bug in the code causing this problem.

Based on my experience with the MiG-21, having flown it since it was released, I vote for number 3. But if it is a bug, there should be a way to replicate it so that the programmers can confirm and fix the problem.

If it happens again, I will look for odd hydraulic indications. But the other night, I had full control of the aircraft, I just didn't have landing gear, brakes, or drag chute deployment, and incorrectly assumed all three were tied to the loss of air pressure. I saw no evidence of loss of hydraulic pressure as my controls worked perfectly. I used the emergency gear deployment levers and the emergency brake lever, so I landed just fine. But I didn't think twice about the gear not deploying until I read this series of posts.

If you have the track you can always post it

So apparently I didn’t misremember lol! Some weird stuff going on.

On a side note, I love doing space runs up to 100k feet. It always flames out, and Im often out gas, so I usually deadstick it to the nearest airfield. Only recently have I noticed that I slowly lose hyd pressure with the engine off (with corresponding readings on the gauges), causing me to crash as I line up for final. I dont recall losing flight control due to hyd pressure loss when engine is off. Has this been recently implemented? Maybe somehow related to the gear failures?

You might be losing enough speed to stop the engine windmilling enough to preserve the pressure, maybe.

I flew the exact same mission I flew the last time I left the gear lever up and had the gear fail: Instant Action Nevada Interception. I intentionally left the lever up until on final approach. Landing gear worked just fine.

I don't have a track saved from the time it failed.

The intercept mission requires a steady climb to 11km with pretty much continuous use of afterburner. So what aspect of that mission profile could cause a valid landing gear failure as opposed to a random bug in the simulation's gear logic?