Forward Flight problems

Service and maintenance tips, questions, and issues.

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Forward Flight problems

Postby G-ATLO » Wed Jan 22, 2014 3:47 am

Im still having a problem in forward flight and don't understand why. I took the Helicopter for service last year and when I picked it up it flew horrendously. While in for its service it had its Pylon bearing shafts replaced and according to my service dept they changed nothing else and rebuilt it the same as they took it apart. Before they had it it flew really well but now constantly pitches up to the point that its tiring to fly. They spent hours messing about tracking etc but eventually I had to call and end to it because it wasn't improving and I was just wasting money. I mentioned this last year on the forum and tried everything mentioned but if anyone has any other ideas I would really appreciate it many thanks Neil.
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Re: Forward Flight problems

Postby 9121u » Wed Jan 22, 2014 7:26 pm

Possible causes blades mixed up from there original position like red with red yellow with yellow ext../inboard nuts not torqued right bearings to be loose..../ bearings ran out of grease..o'rings on inboard blades did not seal and all the grease flew out.... does it helicopter bounce up and down on run up ...need more info on what it does exactly from run up to hover and flight what it does in each order.?.... need to know this to determine problem or everyone's guess
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Re: Forward Flight problems

Postby G-ATLO » Thu Jan 23, 2014 3:07 am

Thanks for trying to help, I will check all you have suggested next time I fly , but judging by the weather here in the UK at the moment its not going to be anytime soon . I think it bounces on run up but to be honest I haven't flown it much this Annual as its to much like hard work . The sad bit is that it flew like a dream before they changed the Pylon bearing shafts . I have checked and adjusted the electric trim to exhaustion but Im convinced its something reassembled not exactly the same.
Funny all the problems Ive had over the years have been after maintenance and things being disturbed, irony eh.
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Re: Forward Flight problems

Postby Brad Bowles » Thu Jan 23, 2014 5:35 pm

Did they replace thrust bearings? If so are they installed correctly ? Maybe a phase issue at the hub. Has the balance been checked and if so what are the readings? I would have in board blades pulled and start from zero.
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Re: Forward Flight problems

Postby 9121u » Thu Jan 23, 2014 6:15 pm

I agree with Brad take it back apart and start over I have never heard of a problem of that kind ....good luck
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Re: Forward Flight problems

Postby seneca2e » Fri Jan 24, 2014 9:00 am

If it flew fine BEFORE the maintenance then something was done wrong in all probability during the maintenance. Sometimes over the years we've had unrelated things occur during maintenance that appear like Kremlins BUT the vast majority of the time a new problem traces directly back to what was done. I'm convinced the installation of the pylon bearing shafts, installation of the bearings, subsequent messing around trying to track the problem, etc lies at the heart of your problem. Sometimes it doesn't take much to make these things radically different. In my own case we tried a new blade and no amount of tracking and balancing would get the machine back to the flight characteristics it had before the blade was changed. We put the old blade back on with almost no tinkering and it was right back to flying fine. Sometimes a set of blades just flies better together and no amount of messing with them when you introduce a different blade in the mix works as well. I know you didn't change a blade but you did change the pylon shafts and bearings(which can be put in backward as well as the seals and it is very easily done). I think your problem lies with the work you had done. I'd go back to that point and redo it.
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Re: Forward Flight problems

Postby seneca2e » Fri Jan 24, 2014 9:07 am

Tom since it's slow on the forum anyway can you post what you're thinking if say the helicopter does bounce up and down on runup. What are you thinking at that point? In an Enstrom it's going to be the strut oleo pressures or blade dampers needing bled for sure but in a Brantly what are you looking at? I guess we're assuming the blades are not way out of track and balance at this point so what does he do now?
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Re: Forward Flight problems

Postby G-ATLO » Fri Jan 24, 2014 10:44 am

Thanks to everyone for there input very much appreciated ,I think it may have to wait until the annual in April as costs for maintenance to correct work is just painful. I have never worked out in Aviation when mistakes are made by an engineer I have to pay over £50 an hour for him to work out where he went wrong, would you pay an automotive guy money to get your car to start if you only took it for tires? And helicopter companies produce time lifed parts that fail prematurely then you have to go and buy new ones ,never understood it.
Oh and seeing as a few of you are reading get this if you think you sometimes have it bad from the FAA, The CAA have for many years been trying to harmonize with Europe .On the first go it was called The JAR about 10 years ago and everything was changed. Now they have decided its going to be called EASA. All the regulations are being changed to try and bring everyone into line maintenance, Aircrew certification etc.
On going for my Annual check ride this year with a friend who runs a flying School (that I Lent my Brantly too so he could be checked out by the retiring only other person able to check me in the UK) He told me that the CAA have told him due to new rules he cannot check me out .On his enquiry as to who could check him out he was told they don't know and that was last August since when nothing has happened.
So I had a check ride as normal but am now flying a UK Registered Helicopter on an American commercial god bless the FAA. So if ever your feeling pissed off with the FAA just think in the UK there is no one to give you a check ride, oh and Avgas is now over £2.00 a litre (yes that's a litre).Go and do the conversion the cost will make your eyes water all the best Neil.
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Re: Forward Flight problems

Postby seneca2e » Fri Jan 24, 2014 10:20 pm

Neil,
Are you saying that in all of England there's not one person that can check someone out in a Brantly? They used to be very popular there and I thought there was still a small following of the mark. Shocking that there is no one at all to do it. We do complain about prices on fuel and maintenance over here and it's getting worse but of course not as bad as overseas most places.

As to your predicament it does really hurt to pay money and get bad results. It happens though as sometimes it's just hard to pinpoint a problem with certainty and it becomes necessary to R&R-trial and error if you will. Hope you get it lined out and flying great in the near future. Please be sure to update the thread as you do various things to cure the problem.
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Re: Forward Flight problems

Postby G-ATLO » Sat Jan 25, 2014 3:03 am

Yes I am saying that there is now no one to check you out here in the UK at all. I had the guy who runs the helicopter museum in Weston get intouch as he runs a Brantly and he to was amazed there is no one to check anyone, and he knows everyone. As to maintenance I think the problem is that my last Annual was over £4000 and they didn't do anything out of the ordinary so god knows how much this is going to cost.
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Re: Forward Flight problems

Postby Brad Bowles » Sun Jan 26, 2014 7:27 am

How many Brantlys are still flying in the UK?
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Re: Forward Flight problems

Postby G-ATLO » Sun Jan 26, 2014 10:19 am

As far as I know 3 possibly 4,two were written off by the same bloke within months of each other who decided he knew everything about helicopters because he had flown an S76 out to the rigs for years. He started a small flight training thing but clearly never read the manual for the Brantly, as while he was giving a guy his annual check ride in this guys Brantly he announced that he was going to throttle chop him, to which he argued that it clearly states in the manual not to chop but roll back to idle. They argued and the examiner chopped the throttle , the engine stopped and they were committed to a real unprepared auto to which he hadn't expected. They ran on at the end of the auto hit a runway light on a disused runway were he was operating from and rolled it over.
The other was with a student allowing him to lose the tail rotor before arresting the turn near the ground an rolling it over. And I would bet money he blames the Brantly .Its not the first time I've heard of this kind of thing ,a high time 747 pilot / Helicopter/ Examiner in Australia a came across was leaning the mixture in the hover on the Brantly. I know two here on the UK register that can Fly mine included, and one on the US register(that's the guy who had his Brantly wrecked by the Useless Examiner .The other possible keeps being sold appearing and disappearing ,Ive never seen it fly, and alovely original one in Devon in a hangar that has also an expired Cof A
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Re: Forward Flight problems

Postby Brad Bowles » Sun Jan 26, 2014 7:55 pm

If you keep your US FAA rating current will this allow you to fly your UK registered ship with out a check ride from an examiner there? What happened to the ships that were wrecked? I had 4 gentlemen from the UK that came over to fly with me in mine last year. They come to the US a few times a year to fly in different older aircraft.
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Re: Forward Flight problems

Postby G-ATLO » Mon Jan 27, 2014 2:51 am

Yes that's what Im doing,I can fly on either my US or Australian License but I don't think the other guys have any other license .As to the wrecked Brantlys I have no idea what happened to them ,but the one guy who was on the check ride bought another straight away so I assume he had any parts that were of use.
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Re: Forward Flight problems

Postby bryancobb » Wed Feb 05, 2014 4:50 am

Back to your original post and the problems after maintenance.
** Did the mechanics have the Maintenance Manual IN THEIR HANDS as they replaced your Outer Pylon Bearing Shafts?

If they were strictly told to ONLY do necessary work related to the OPBS's, they would have:
1) Removed AN-3 Damper bolt from T.E. from each blade
2) Remove Outer blade pivot bolt and remove each of the three outer blades
3) Remove two screws and remove grease retainer disc from each blade accessing blade retention nut
4) Disconnect each Pitch Link from each Inner Blade Pitch Horn (WARNING: use the correct thickness of conical washers when re-installing and MAKE ABSOLUTELY CERTAIN the two ears of each Pitch Horn are NOT squeezed together as the AN-4 bolt is torqued...THEY WILL BREAK OFF)
4) Remove Blade Retention Nut and carefully remove each inner blade from pylon by pulling outward

From that point the OPBS's can be removed and replaced by drilling out the single Keeper Rivet and unscrewing the shaft.

Here's some of my thoughts about what could have happened to cause your problem.
* They "probably" didn't touch or disturb the 4 feather bearings in each blade. These bearings are hard to get out and they come off when the inner blade is removed and they all 4 stay up inside the blade.
* There's a very thin single feather bearing, and a rubber Rain Seal at the ROOT of each inner blade. If The rubber seal is old, it can crumble into pieces. The inner blade relies on the thin bearing and the rubber rain seal to center the root of the blade on the pylon and keep it centered as cyclic and collective moves the pitch horn. The rubber rain seal may not be centering the blade on the pylon and could be your problem on one or more blade.
* If any ears are cracked or broken off any pitch horn, That could be the your problem.
* Inner blades MAY have been re-installed in another position from where removed.
* An inner or outer blade could have been unknowingly damaged during removal or installation.
* Seems like I remember reading SOMETHING about Outer Pylon Bearing Shafts that were manufactured with CUT THREADS and ROLLED THREADS. The ones with ROLLED THREADS are the only airworthy ones and that same letter spoke about how to install them while insuring their base flange contacts the tip-end of the Pylon Tube at all 360 degrees around, as it is screwed in. That is sooooo critical and IF yours didn't, the OPBS MAY be cocked to one side and not parallel to the Pylon Tube centerline. This would make feathering be "notchy" and could cause your problem. (Where did you get your OPBS's that you had them install?) I had a BRAND NEW uninstalled set with rolled threads that I bought from Brantly in 2003. They are SOMEWHERE right now with the new owners of N2175U, I suppose?
* An OPBS retaining nut COULD HAVE been left loose.

THAT'S ALL I CAN THINK OF
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