Go Back  PPRuNe Forums > Aircrew Forums > Rotorheads
Reload this Page >

S-300C (Lycoming HIO-360-D1A) > 2000rpm w/o load => overspeed

Rotorheads A haven for helicopter professionals to discuss the things that affect them

S-300C (Lycoming HIO-360-D1A) > 2000rpm w/o load => overspeed

Old 25th Jul 2012, 12:15
  #1 (permalink)  
Thread Starter
 
Join Date: Feb 2012
Location: LOWW
Posts: 300
Question S-300C (Lycoming HIO-360-D1A) > 2000rpm w/o load => overspeed

The S-300C has a four cylinder Lycoming HIO-360-D1A engine.
Engine rpm green arc sits around 3200 rpms.

Why is exceeding 2000 rpm without load considered overspeeding?

FM:
IF ENGINE RPM EXCEEDS 2000 RPM WITH
ROTOR DISENGAGED INSPECTION OF DRIVE SHAFT
IN ACCORDANCE WITH HMI APPENDIX B IS
REQUIRED BEFORE ANY FURTHER OPERATION
What engine parts might be damaged?

I find that very astonishing, considering that all cams, crank and shafts are built for sustained 3200 rpm;
and I do like to understand the reason for a rule, helps memorizing it a lot.

Last edited by Reely340; 25th Jul 2012 at 12:20.
Reely340 is offline  
Old 25th Jul 2012, 14:28
  #2 (permalink)  
 
Join Date: Jun 2012
Location: North America
Posts: 20
Quote: Why is exceeding 2000 rpm without load considered overspeeding?

Because it is stated in the manual.

HOW DARE YOU QUESTION SIKORSKY!!! (just kidding)

In my recollection from my training days I believe it is the short-shaft that needs to be inspected. It's the shaft that comes out of the engine connected to the lower pulley that you turn each way and listen if there is a clanking noise (metal on metal). Not sure why in a no load situation it needs to be checked.
OffshoreHeli-Mgr is offline  
Old 25th Jul 2012, 14:31
  #3 (permalink)  
 
Join Date: Nov 2006
Location: After all, what’s more important than proving to someone on the internet that they’re wrong? - Manson
Posts: 1,512
RTFQ

What engine parts might be damaged?
None.

IF ENGINE RPM EXCEEDS 2000 RPM WITH
ROTOR DISENGAGED INSPECTION OF DRIVE SHAFT
IN ACCORDANCE WITH HMI APPENDIX B IS
REQUIRED BEFORE ANY FURTHER OPERATION
It is the little drive shaft between the engine and lower pulley that requires a crack check and visual inspection. P/No. 269A5559-003 as indicated below.

RVDT is offline  
Old 25th Jul 2012, 14:34
  #4 (permalink)  
 
Join Date: Oct 2006
Location: Florida
Age: 55
Posts: 193
I'm not sure exactly what happens that causes damage, but I do know the drive shaft (they always called it the "short shaft") has to be inspected by doing a magnaflux test to check for cracking. On newer models, the mags will short out if you try to roll the throttle on without the rotors engaged. You can expect the aircraft to be down for a couple of days, minimum.

BTW- Don't break it as Schweizer lists the part for $20,077.33!

Last edited by helonorth; 25th Jul 2012 at 14:45.
helonorth is offline  
Old 25th Jul 2012, 14:57
  #5 (permalink)  
Thread Starter
 
Join Date: Feb 2012
Location: LOWW
Posts: 300
While I do believe y'all to be right, I have a hard time seeing why that "lower pulley coupling shaft" so urgently needs inspection when it only sees a minimum load (drag of the lower pulley bearing) while hitting 2200 rpms.
We recently had anohter 300C "completely apart" (600h, recently bought from foreign owner G-xxx) and the mechanic showed us that very shaft, with its funny curved sprockets, and dumped it into the waste bin together with the splined "axle" of the lower pulley, as their visible wear was way off spec, on both.

Of course I can imagine that compensating for tiny engine movements relative to the frame while transmitting 190 ponies will be hard on the shaft and the splines it connects to.

Could it be that w/o load the shaft would be rattling in the pulley from the engines uneven running, having no big flywheel and lacking load?

btw. our 300C indeed does have that overrevv ignition cut off *cough*
and the FI needs a sturdy device (smartpone will do) to whack the starter relais, to make sure it actually sends electricity to the brand new, shiny high revv starter. Hence that 300C currently requires a crew of two, for startup

Last edited by Reely340; 25th Jul 2012 at 15:04.
Reely340 is offline  
Old 25th Jul 2012, 16:05
  #6 (permalink)  
 
Join Date: Jun 2012
Location: North America
Posts: 20
Quote: BTW- Don't break it as Schweizer lists the part for $20,077.33!

From a business point of view those R22's are looking good.
OffshoreHeli-Mgr is offline  
Old 25th Jul 2012, 16:21
  #7 (permalink)  
 
Join Date: Nov 2008
Location: UK
Age: 62
Posts: 907
So when you are practicing auto rotation, splitting and rejoining the needles involves the engine running over 2,000 rpm and off load too.
So how come you don't need an inspection for this??
chopjock is offline  
Old 25th Jul 2012, 16:27
  #8 (permalink)  
 
Join Date: Feb 2008
Location: UK
Posts: 386
From a business point of view those R22's are looking good.
So, R22/R44s don't have any overspeed issues
FLY 7 is offline  
Old 25th Jul 2012, 16:32
  #9 (permalink)  
Thread Starter
 
Join Date: Feb 2012
Location: LOWW
Posts: 300
269A5559-003 is more like 2796,68

We sure would have had a major "party" complete with pics and gals
when the mechanic would drop a part costing 20 Grand into the bin
in the cause of a 600h inspection

Last edited by Reely340; 25th Jul 2012 at 16:42.
Reely340 is offline  
Old 25th Jul 2012, 16:39
  #10 (permalink)  
Thread Starter
 
Join Date: Feb 2012
Location: LOWW
Posts: 300
So when you are practicing auto rotation, splitting and rejoining the needles involves the engine running over 2,000 rpm and off load too.
So how come you don't need an inspection for this?
Short answer: you don't.
I'm required to split needles at 2500 rpm during preflight engine check to verify correct function of the freewheeling clutch, but then again the rotor has to be engage before doing that check.

That is exactly what puzzles me:
Only when exceeding 2000 rpm w/o having engaged the rotor requires the inspection.

There are students who accidentally switch the ignition to off when testing "left", talk about major needle split
And of course after the magneto check you do freewheeling clutch check mentioned above.

All of that at 2500 rpm, w/o forcing an inspection.
That is was has me puzzled, what the danger/mechanical damage is, with exceeding 2000 rpm, disengaged.

Last edited by Reely340; 25th Jul 2012 at 16:41.
Reely340 is offline  
Old 25th Jul 2012, 18:03
  #11 (permalink)  
 
Join Date: Jul 2004
Location: Germany
Posts: 783
The driveshaft will oscillate, bend and take the shape of a banana.
GoodGrief is offline  
Old 25th Jul 2012, 19:13
  #12 (permalink)  
Thread Starter
 
Join Date: Feb 2012
Location: LOWW
Posts: 300
Cool, got pics?
Reely340 is offline  
Old 25th Jul 2012, 19:33
  #13 (permalink)  
 
Join Date: Aug 2010
Location: In the air or on the ground
Posts: 5
The driveshaft will oscillate, bend and take the shape of a banana.
This is the only correct answer.

Because there is no load on the lower pulley, the pulley will start oscilating on the frequency of the engine. This causes extreme load on the splines of the lower pulley drive shaft (short shaft), resulting in exessive wear and possible creating cracks at the splines.

Why doesn't his happen when i'm perfoming an autorotation?(engine running 1500-2000 rpm);
Because the clutch is still engaged, so there is the drag of the free running clutch and drag of the bearings and that will damp the oscilation(Solid triangle of the drivetrain).
Twinstar355 is offline  
Old 25th Jul 2012, 19:34
  #14 (permalink)  
 
Join Date: Sep 2011
Location: Germany
Age: 39
Posts: 21
Obviously because it damages the PFM circuits.
Shenanigan is offline  
Old 26th Jul 2012, 03:40
  #15 (permalink)  
 
Join Date: Apr 2005
Location: East of the sun, west of the moon, straight on till morning
Posts: 73
Twinstar is correct if memory serves.

All I would add is that I was once told by one of the tech reps that it was predominately a characteristic of the earlier short shafts that were a bit lighter in design hence easier to damage. I've never heard of one of the beefier ones being damaged, still, follow the manual!
fling-wing_1 is offline  
Old 26th Jul 2012, 17:16
  #16 (permalink)  
 
Join Date: Dec 2005
Location: England
Posts: 1,249
The explanation given to me was that the shaft would behave like a skipping rope during an overspeed but would normally return to shape after the event.
However the damage would manifest itself as hairline cracks along the shaft midway between the splined ends i.e at the point of maximum whip.
Hence a requirement for a magnaflux NDT inspection.

I suppose that if the overspeed was large enough then it might indeed assume the shape of a banana, but then you wouldn't need an NDT!!!

Last edited by ericferret; 26th Jul 2012 at 17:30.
ericferret is offline  
Old 26th Jul 2012, 20:31
  #17 (permalink)  
 
Join Date: Jul 2004
Location: Germany
Posts: 783
I guess Gordy would have pictures.
GoodGrief is offline  
Old 26th Jul 2012, 23:49
  #18 (permalink)  
 
Join Date: Apr 2007
Location: Out there
Posts: 258
During autorotation the shaft is under tension from the drive belts being engaged.
Evil Twin is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.