correct as is Mast bump more frequently after update

[gonzolofogous]

I'm experiencing mast bumping way more frequently after the March performance update. Even sometimes in level flight the rotor separates from the mast. I'll notice it's prominent going from a left bank to a right bank at about 40 kts with the same pitch input. Before the update, I would have to maneuver aggressively to induce a mast bump, but with this update, it seems to happen under normal flight characteristics. Any input would be appreciated,

Tomcat 1-1 

[MoleUK]

I have no idea how you're pulling that off honestly. I have had the complete opposite experience, mast bumping is far, far rarer than it used to be when pushing the engine limits.

Are you running at 100% collective or something?

[gonzolofogous]

No where close to 100%, 80% max is all I'll ever do. I can check my axis to make sure, but it even happens at slow speed ~60 kts with 50% collective

[MoleUK]

Definitely double check and get a track if you can, will take a peek. I've been throwing about the huey pretty aggressively ever since the engine update and almost never mast bump unless I pull way too hard with too much collective.

[gonzolofogous]

Made a video of the mast bump issue. Sometimes I am flying aggressively, sometimes it's my bad flying, but the issue seems to be at high angles of bank, around 90 degrees.

The issue I'm talking about can be found at 3:10 in the video. High angle of bank with aft cyclic at about 70 kts. 

This is the 5th takeoff in the video. The issue seems to happen again at 3:40 and at 4:45

Am I just being too aggressive with it? Helicopters should be able to handle high bank angles.

 

 

Edited January 6 by gonzolofogous

[cw4ogden]

@gonzolofogous

Mast bumping almost always implies a negative G situation.  Best way to visualize mast bumping is to picture pushing your rotor shaft upwards into a tilting see saw.  If you push hard enough, the rotating see saw eventually will tilt enough that it contacts the rotor shaft, aka mast bumping.
 

What I see in your video appears more like some kind of structural failure.  I guess that could be how they have mast bumping coded, but I'd suspect over G or some kind of other limit being broken.  If your G loading is above Zero, as it looks in your video, it's almost certainly not mast bumping.

Edited January 6 by cw4ogden

[Tholozor]

 

[MoleUK]

58 minutes ago, gonzolofogous said:

Made a video of the mast bump issue. Sometimes I am flying aggressively, sometimes it's my bad flying, but the issue seems to be at high angles of bank, around 90 degrees.

The issue I'm talking about can be found at 3:10 in the video. High angle of bank with aft cyclic at about 70 kts. 

This is the 5th takeoff in the video. The issue seems to happen again at 3:40 and at 4:45

Am I just being too aggressive with it? Helicopters should be able to handle high bank angles.

 

 

 

It's not just that you're being aggressive, you're yanking from one end entirely to the other in a pattern that doesn't make too much sense in flight. You can bank at hard angles, but you don't want to suddenly yank the stick from full right to full left without torque and collective adjustments while in a right turn.

Are you using keyboard controls?

Edited January 6 by MoleUK

[MoleUK]

43 minutes ago, cw4ogden said:

@gonzolofogous

Mast bumping almost always implies a negative G situation.  Best way to visualize mast bumping is to picture pushing your rotor shaft upwards into a tilting see saw.  If you push hard enough, the rotating see saw eventually will tilt enough that it contacts the rotor shaft, aka mast bumping.
 

What I see in your video appears more like some kind of structural failure.  I guess that could be how they have mast bumping coded, but I'd suspect over G or some kind of other limit being broken.  If your G loading is above Zero, as it looks in your video, it's almost certainly not mast bumping.

 

4:46 to 4:48 is fairly distinctive. He's just about to start going into a negative G situation which you can obviously get through if you keep pulling through it. But if you totally reverse the stick in that situation from right to left (and with no torque adjustments) it's going to cause problems.

[MoleUK]

Hah. this actually explains a mast bump I had a few weeks back I think. Wasn't entirely sure what I did there as it was the first time it'd happened in months.

Unfortunately the controls aren't captured at the moment it bumps, but it looks the same. In a hard right bank but not pulling hard enough into it, and then a quick hard left on the stick.

This is not the way you want to turn, here I was just trying to get out of the rocket splash and continue forwards so I probably pulled left stick instead of continuing into the right turn.

 

Edited January 6 by MoleUK

[BIGNEWY]

Hi, 

we have made no changes to the DCS: UH-1H flight model in the recent patches. 

Please include a short track replay example showing an issue and we will investigate. 

thank you 

[gonzolofogous]

UH-1-rotor-failure.trkAttached is a short track failure from takeoff to rotor failure

1 hour ago, MoleUK said:

It's not just that you're being aggressive, you're yanking from one end entirely to the other in a pattern that doesn't make too much sense in flight. You can bank at hard angles, but you don't want to suddenly yank the stick from full right to full left without torque and collective adjustments while in a right turn.

Are you using keyboard controls?

 

I'm using thrustmaster warthog controls. In a right bank, the left counter input is needed to stop the rate of bank and hold a constant bank. It seems this isn't a mast bump issue and more of a structural, rotor failure issue, so would I need to lower collective to reduce rotor stress? If that's the case, It would also tend to overspeed the rotor system

[gonzolofogous]

1 hour ago, MoleUK said:

Hah. this actually explains a mast bump I had a few weeks back I think. Wasn't entirely sure what I did there as it was the first time it'd happened in months.

Unfortunately the controls aren't captured at the moment it bumps, but it looks the same. In a hard right bank but not pulling hard enough into it, and then a quick hard left on the stick.

This is not the way you want to turn, here I was just trying to get out of the rocket splash and continue forwards so I probably pulled left stick instead of continuing into the right turn.

 

 

I'm not all too familiar with the hind and I can't see from the video, but with how much the hind is shaking, are you close to Vne, max speed? 

Edited January 6 by gonzolofogous

[MoleUK]

24 minutes ago, gonzolofogous said:

UH-1-rotor-failure.trkAttached is a short track failure from takeoff to rotor failure

I'm using thrustmaster warthog controls. In a right bank, the left counter input is needed to stop the rate of bank and hold a constant bank. It seems this isn't a mast bump issue and more of a structural, rotor failure issue, so would I need to lower collective to reduce rotor stress? If that's the case, It would also tend to overspeed the rotor system

I don't think lowering collective will stop this. You're barely using any.

You don't need that much left input, you're going from almost full right to full left within 1-2 seconds.

When in that hard right turn, you're just starting to tilt over into a position where you'd be in negative G. If you keep pulling through it you avoid popping. If however you suddenly yank the stick all the way left, I suspect it thinks (or you are for a moment) you're hitting negative G and pops.

This does explain a few odd bumps I've had that I assumed was because I was pushing the collective too hard.

12 minutes ago, gonzolofogous said:

I'm not all too familiar with the hind and I can't see from the video, but with how much the hind is shaking, are you close to Vne, max speed? 

 

That's a Huey i'm flying, not a hind. I'm usually cruising at 140-150 knots.

You can generally push the collective very hard and run very heavy. But if you yank left/right like that in a turn you will most likely keep popping. Use gentler movements, and use your pedals.

Oh, and don't run the Huey light. You really want to be runnning it very, very heavy atm.

Edited January 6 by MoleUK

[MoleUK]

I hadn't seen the beginning of the video. No wonder your inputs are over the top, you've messed with the axis saturation in a way that isn't helping at all. Small movements are going to max out your pitch and roll axis. I'd undo that to start.

Edited January 6 by MoleUK

[gonzolofogous]

19 minutes ago, MoleUK said:

I hadn't seen the beginning of the video. No wonder your inputs are over the top, you've messed with the axis saturation in a way that isn't helping at all. Small movements are going to max out your pitch and roll axis. I'd undo that to start.

 

I modified the axis inputs limiting the saturation and it's still affected.

My current settings for X roll axis are Saturation X 100, Saturation Y 56 and 26 on the curves. 

After looking in the recordings and messing around with it more, it seems to happen when going from a left > 60° bank to a right > 60° bank. In that right bank, the huey pitches up about 20° so forward pressure is needed to keep level. I think in this forward input is when the rotor separation is happening. Maybe with this forward input, it's thinking there's negative Gs on the mast or something

I'll work on posting another video and track.

[gonzolofogous]

UH-1-rotor-failure2.trk

Attached is a youtube video and track file. Please ignore my terrible "hovering". With the inputs toned down, it seems to happen with high bank angles.

 

[Flappie]

A few milliseconds before your mast bump:

It is true the big 2023 Huey update causes more frequent mast bumps. But is it unrealistic?

I wouldn't want to be the helicopter in your track.

[Vakarian]

You need to be waaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaay less aggresive on your controls

[MoleUK]

16 hours ago, gonzolofogous said:

UH-1-rotor-failure2.trk 198.54 kB · 1 download

Attached is a youtube video and track file. Please ignore my terrible "hovering". With the inputs toned down, it seems to happen with high bank angles.

 

You're still being way too aggressive going from one end to the other, and it looks like you've still got something going on that is exacerbating the excessive movement on the axis. Either because of a curve or because of saturation or both.

Edited January 9 by MoleUK

[BIGNEWY]

Fly smooth, treat the bird well and you will be fine.

[Hiob]

17 hours ago, gonzolofogous said:

UH-1-rotor-failure2.trk 198.54 kB · 1 download

Attached is a youtube video and track file. Please ignore my terrible "hovering". With the inputs toned down, it seems to happen with high bank angles.

 

Dude, try to fly as if you want to get somewhere alive. That will prevent your chopper from mast bumping. You're driving a helicopter not a drone!

Edited January 9 by Hiob

[Xupicor]

On 1/6/2024 at 10:51 PM, MoleUK said:

That's a Huey i'm flying, not a hind. I'm usually cruising at 140-150 knots.

That's awfully fast for a Huey. Comfortable cruising speed is somewhere around 90 kts, usually speeds above 115-125 kts are literally off the charts (on performance charts for UH-1H), 140-150 kts is in some serious overspeed territory, I'd say. Turning with those speeds alone will give you trouble if it's not smooth. As you know, jerking the cyclic even with much lower speeds is not a good idea.

 

On 1/8/2024 at 6:25 PM, gonzolofogous said:

Please ignore my terrible "hovering". With the inputs toned down, it seems to happen with high bank angles.

1. We can ignore the very chaotic hover but you shouldn't. Start with smooth take off into hover. Slowly raise collective, at some point you'll be light on your skids - stop there and find a good stick and pedals position where the helicopter doesn't move, then slowly raise collective and correct as needed. This will teach you to do smaller corrections, smaller movements. It's a foundational thing, learn to fly a smooth stable hover, fly around slowly in ground effect, maybe 10 feet over the ground. You're moving the cyclic forward and aft A LOT, looks like large overcorrections, basically the helicopter is doing whatever it wants and you're behind the curve trying to react -- you need to be in control, you need to smooth it out and then with practice you'll be able to predict what the helicopter is going to do with a given input. For the moment just start with stable hover and slow taxing around to where you want to take it.

2. Just before you mast bump you enter a turn at quite a bank angle and what causes the mast bump directly is your momentary movement of the cyclic forward - you enter into negative G territory which is not something you want. If you have to enter in such a high bank angle turn then don't try to leave it early by pushing the stick forward. Take the turn into completion, the moment you enter such a turn you have to smooth your controls out. Keep the back pressure through and slowly bank out of the turn back into level flight. Any abrupt forward cyclic movement risks instant mast bumping in that situation.

Let me quote the UH-1H Operator's Manual:

Quote

5-12. Prohibited Maneuvers.
a. Abrupt inputs of flight controls cause excessive
main rotor flapping, which may result in mast bumping
and must be avoided.
b. Intentional maneuvers beyond attitudes of +/- 30
degrees in pitch or +/- 60 degrees m roll are prohibited.
c. Intentional flight below +0.5 G is prohibited.

Now just think how many times you break those in that clip. I'm not saying you can't break the rules, but if you turn 60-90 degrees bank, pull hard on the cyclic and then release it a bit -- you're at a very high risk of immediate mast bump. That's basically going a) b) c) on that list. : )

That's why I recommended above to focus on hover and taxi to smooth over your controls first.

For a slick, this is more or less the controls for hover. If you set them close to this before you pull on the collective you should be less likely to veer off in any direction. Your situation will of course be different every time, but it's roughly "a bit" aft and left.

Edited January 13 by Xupicor

[MoleUK]

On 1/13/2024 at 12:00 AM, Xupicor said:

That's awfully fast for a Huey. Comfortable cruising speed is somewhere around 90 kts, usually speeds above 115-125 kts are literally off the charts (on performance charts for UH-1H), 140-150 kts is in some serious overspeed territory, I'd say. Turning with those speeds alone will give you trouble if it's not smooth. As you know, jerking the cyclic even with much lower speeds is not a good idea.

Yeah currently it gets faster the heavier you load it. Obviously it's not meant to but it's the way it's been since the engine update, to reach that sort of cruise speed you want to weigh around 12,500lb's. Though you can get closer to 14,000 iirc and still hit it fine.

There is no overspeed for the Huey anymore, at least as far as i'm aware. Haven't seen how fast it can go in a dive though. Seems fine in excess of 300 kph.

But it flies surprisingly well at those speeds, so for now i'm going to continue flying it that way until there's another pass on the engine/flight model. It's been a fun time flying her while she's fast.

Though there are plenty of charts listing the top speed at 140+knots in low level flights, just not when you're seriously overloading the weight. And as ever there is what the frame is actually capable of and what the documentation suggests not to exceed for maintenenance and safety reasons etc. Neither of which we necessarily have to abide by.

Regardless, the old engine model seems to have definitely been severely underpowered. And I will enjoy the current engine power while it lasts, as lopsided as it may be.

 

Edited January 14 by MoleUK

[Zap921]

These folks got the explaination of your problem correct.  Set your axis settings back to default.  Your x/y axis take you straight to max left/right with a tiny movement, way easier to learn to fly at default settings then tweak.  Get your feet on the pedals and trim the aircraft using the ball.  Try 90 knots max for usual point to point top speed.  Learn to hover first and watch some videos on how much control input looks normal, pulling 1,000ft  per minute and whipping her left to right like that would rip any helo apart.  No offense, but start slow.  It's a great, classic bird that is a proven workhorse.  Good luck, you'll get it.