Blades Breaking on the Pad

[martinistripes]

Not sure what's causing this at all. Maybe random failures setting.

 

I created a mission starting cold on the pad at Batumi. I start the APU and the blades start turning (yes, before even starting an engine) and then snap. It's happened on several occasions consecutively. Not sure if I'm doing something wrong or it's a bug.

 

I'll post a track later (I'm away from home now).

 

I set the temperature to -15. Is it something to do with ice on the blades maybe, but still I don't understand how they would turn or snap after starting the APU.

 

It could be a random failure, but it dosn't seem likely when it occurs 3 times in a row.

[EtherealN]

What are the wind speeds?

[martinistripes]

6 m/s

12 m/s

18 m/s

[Pyroflash]

Are you sure it is your blades breaking? Failure to start engines can result from a number of different things. Check inverter to standby. Check throttles to OFF before starting APU. Check main and wing fuel boost pumps ON. Check TK Gate and Cross Feed switches OFF.

 

-15 isn't exactly a "cold" temperature as far as the aircraft goes, so it probably isn't that. I have noticed that sometimes the blades will turn a little before you start the engines. This is NORMAL, just make sure your instruments are in the green before starting.

[martinistripes]

Thanks Pyroflash, but I'm sure it's the blades. The aircraft begins to wobble then I switch to the external view and see some blades are half length with the debris on the floor.

 

I'll repeat and record of course.

 

Now, I'm going to look for a cold beer in Sri Lanka. :smilewink:

[MTFDarkEagle]

Ryan: try to replicate. If so, also post a track when possible and we'll have a look.

[Isegrim]

Screenshots would also be helpfull maybe its a proplem with a broken installation or something the Track dont show cause its working normal on other Machines.

 

Cross Feed switches on or off doesnt make a difference on a new Shark.

The Engines should start also with X feed on.

Im just saying that cause i always do that:smilewink:with X feed on.

[AlphaOneSix]

Leave the rotor brake on until the instant before you press the engine start button. I'm assuming that you're turning off the rotor brake and then starting the APU. It's turning off the rotor brake that allows the rotors to spin, not starting the APU. By turning off the rotor brake at the last moment prior to pressing the engine start button, the rotors have less time to start doing anything funky, and during engine start, they will quickly build up enough speed where the wind won't affect them as much.

Edited February 8, 2012 by AlphaOneSix

[martinistripes]

Ok, here's a track.

 

I realise I didn't start-up as per the book by the way, but I'm still not sure that accounts for my blades snapping the way they are.

 

You can see the blades begin turning at some speed and all I did was start up the APU. :huh:

Rotor Failure.trk

[martinistripes]

The only mod I'm using (and have used with this particular install) is the one that converts the EKRAN voice to Russian. Otherwise, it's clean.

[mvsgas]

Looking at your track, I believe this issue has been identified previously and WIP to be fix by ED team. Not sure the cause. I hope this helps.

[AlphaOneSix]

There is no problem here, no bug, no nothing, there is just too much wind.

 

Ok, here's a track.

 

I realise I didn't start-up as per the book by the way, but I'm still not sure that accounts for my blades snapping the way they are.

 

You can see the blades begin turning at some speed and all I did was start up the APU. :huh:

 

Directly above your post, I posted the reason it was happening as well as one way to get around it. You must not have read it so I'll quote it here again:

 

Leave the rotor brake on until the instant before you press the engine start button. I'm assuming that you're turning off the rotor brake and then starting the APU. It's turning off the rotor brake that allows the rotors to spin, not starting the APU. By turning off the rotor brake at the last moment prior to pressing the engine start button, the rotors have less time to start doing anything funky, and during engine start, they will quickly build up enough speed where the wind won't affect them as much.

 

I watched the track. The instant the blades started to move, I took control and immediately turned the rotor brake back on (you had already released it, which is fine in accordance with the proper startup procedure, but that actually hurts you in this case). When I turned the rotor brake back on, the blades stopped turning. I then continued the startup procedure from there, and left the rotor brake on until right before I started the first engine. In other words, I click off the rotor brake, then immediately press the first engine start button. The first engine starts and I continue the startup as normal, with no blade problems.

 

TL;DR

 

You have two choices, read my explanation and follow my suggestion, or edit the mission and reduce the wind velocity.

[martinistripes]

Sorry AlphaOneSix. I was not being ignorant to your post. I understand that using the rotorbrake will avoid the situation.

 

But I don't understand the mechanics of what's happening, and why it's happening. To me, it still appears bugged.

 

Would my wind speed of 6 m/s begin to turn the blades like that? Perhaps so.

 

But would the blades really snap, just from being turned by the wind? :huh:

 

I'm assuming they would withstand much greater forces under normal use.

[martinistripes]

There is no problem here, no bug, no nothing, there is just too much wind.

 

 

So what you're basically saying is, it's normal for a 6 m/s wind (moderate breeze by the Beaufort Scale) to snap a rotor blade in two if someone were to leave the rotor brake off?

[Eddie]

Yes. It's not the fact that the rotors are spinning that is the problem. The problem is that the rotors are flexing in the breeze, AND because they are spinning while doing so the upper and lower rotor blades can/will collide.

 

Think about when you used to wobble a ruler in your hand as a kid at school, it'd start flexing up and down more and more the longer you wobbled it. The rotors do the same, and the low rotation speed produced by the wind isn't enough to generate the lift/centrifugal force needed to stabilise the blades.

 

Hence stopping them spinning until you acutally start the engines means that they don't have time to felx as much before the rotors spin up and the lift counteracts the wind flexing the blades.

[martinistripes]

Then, it seems I've just been educated. Interesting to know. I never would have guessed the blades to be so fragile.

[AlphaOneSix]

The blades aren't really that fragile, but if they collided in real life, there would be at least a little bit of damage that would very likely render the aircraft unsafe to fly. There isn't really a partial damage model for the rotor blades that I'm aware of in-game, so the only solution is to just break them in half.

 

6m/s probably should not have so great an effect on the blades, 12m/s might, I'd say it's possible...and 18m/s is like asking Mother Nature to have her way with you.

 

Slightly off-topic trivia: Many helicopters these days have an option for a gust lock that allows you to keep the rotor brake on during engine start, allowing the engines to come up to idle without the rotors moving at all. Then the brake comes off and the blades spin up very quickly, drastically reducing the possibility that the wind will cause a blade to do any damage (which usually means striking the tail boom on a single rotor aircraft). I have been in the middle of a microburst with an Mi-17 trying to tie down the rotor blades, and the wind just twisted the rotor (with the rotor brake on) and one of the blades smashed into the tail boom. It was neat to watch but it sucked to fix.