Robinson R22 Corner [Archive copy]
Senis Semper Fidelis
Join Date: Feb 2001
Location: Lancashire U K
Posts: 1,288
Likes: 0
Received 0 Likes
on
0 Posts
Here in the UK we have some very cold and damp days, especially at this time of year, I feel that if you didn't run the fuel out of the system before earthing your mags it could store a problem for the next time the craft was started up, with the possibility existing that the previouse or next pilot could/be a student who left the throttle open enough to cause some initial start up possibility of an overspeed, also excess fuel could drain into the oil and create an explosive possibility in the crankcase!. .but why not follow the manufacture's route, and when was the last time anyone was stuck for a wire breakage on the fuel cut off?. . <img src="eek.gif" border="0">
Sorry, I seem to have posted this answer on the wrong thread, should be on Mags shutdown R22, many apologys
[ 24 January 2002: Message edited by: Vfrpilotpb ]</p>
Sorry, I seem to have posted this answer on the wrong thread, should be on Mags shutdown R22, many apologys
[ 24 January 2002: Message edited by: Vfrpilotpb ]</p>
Iconoclast
Join Date: Sep 2000
Location: The home of Dudley Dooright-Where the lead dog is the only one that gets a change of scenery.
Posts: 2,132
Likes: 0
Received 0 Likes
on
0 Posts
To: vorticey
On opposed engines used on a helicopter you do not have the flywheel effect of a propeller but you do have a flywheel which has a relatively high moment of inertia. When you shut down by turning off the mags the engine will continue for several revolutions creating a high vacuum behind the closed butterfly drawing in fuel from the jets. As I had indicated if this fuel is drawn into a cylinder that has a hot spot (carbon build up on the valves or on the cylinder or plug the fuel can ignite. Under normal start-up of the engine the starter is providing the motive power and all cylinders should start firing in sequence after the initial firing of a single cylinder. However, at shut down there might be only one cylinder that fires and it must rotate the crank along with the resistance of the other cylinders and the weight of the rotating mass. This can put a localized torsional stress on the crank and if sufficiently strong can cause the crank to crack. The US Army had a lot of problems on their engines used on the H-13s and the H-23s suffering cracked cranks. Although not from improper shut down but it illustrates that certain conditions can cause the crankshaft to break.
Another problem is fuel entering a cylinder and being ignited by a hot spot while the intake valve is open resulting in a backfire against a closed butterfly valve on the carb.
[ 23 January 2002: Message edited by: Lu Zuckerman ]
[ 23 January 2002: Message edited by: Lu Zuckerman ]</p>
On opposed engines used on a helicopter you do not have the flywheel effect of a propeller but you do have a flywheel which has a relatively high moment of inertia. When you shut down by turning off the mags the engine will continue for several revolutions creating a high vacuum behind the closed butterfly drawing in fuel from the jets. As I had indicated if this fuel is drawn into a cylinder that has a hot spot (carbon build up on the valves or on the cylinder or plug the fuel can ignite. Under normal start-up of the engine the starter is providing the motive power and all cylinders should start firing in sequence after the initial firing of a single cylinder. However, at shut down there might be only one cylinder that fires and it must rotate the crank along with the resistance of the other cylinders and the weight of the rotating mass. This can put a localized torsional stress on the crank and if sufficiently strong can cause the crank to crack. The US Army had a lot of problems on their engines used on the H-13s and the H-23s suffering cracked cranks. Although not from improper shut down but it illustrates that certain conditions can cause the crankshaft to break.
Another problem is fuel entering a cylinder and being ignited by a hot spot while the intake valve is open resulting in a backfire against a closed butterfly valve on the carb.
[ 23 January 2002: Message edited by: Lu Zuckerman ]
[ 23 January 2002: Message edited by: Lu Zuckerman ]</p>
Join Date: Dec 2000
Location: Ask the voices!
Posts: 435
Likes: 0
Received 0 Likes
on
0 Posts
Same here. We were told that the check was to be done at 75% to prevent cooling fan cracks and excessive stresses.
Also something to do with vibration alterations when you do get a duff-un.
"Some days you are the pigeon, some days you are the statue!"
Also something to do with vibration alterations when you do get a duff-un.
"Some days you are the pigeon, some days you are the statue!"
Join Date: Jan 2002
Location: HARROW,UK
Posts: 38
Likes: 0
Received 0 Likes
on
0 Posts
MY THEORY IS THAT CUTTING THE IGNITION SOURCE ALLOWS UNBURNT FUEL MIXTURE TO WASH LUBRICANT FROM CYLINDER BORES CAUSING DAMAGING FRICTION UPON STARTUP,IF THIS OCCURS REGULARY THE RESULT. .WOULD BE PREMATURE WEAR AND LOSS OF VALUBLE COMPRESSION.KEPT IT AS SHORT AS I COULD (COULD HAVE GONE ON & ON ETC).
Guest
Posts: n/a
Every now and then I follow the checklist in the flight manual, even though that seems like an odd habit..... It is based on the belief that the maker of the machine had some thoughts on the matter at hand.
Ever seen a flight manual that called for a mag cut shutdown?? I have not.
Ever seen a flight manual that called for a mag cut shutdown?? I have not.
Join Date: Feb 2001
Location: the other America
Posts: 103
Likes: 0
Received 0 Likes
on
0 Posts
Thanks for the input & yeah Nick it's a bit of a funny habit to follow those pesky checklist (damn where did I leave it).
Also gotten the impression the Manufacturers have a clue as to how best operate the plant to best effect.
Hey by the way Nick I've just read the S92 checkflight (for about the 4th time) again recently. Love the bit where the chase van gets pushed into the ditch. Are you really that slender and sleek or was it the camera angle??????. .lol
Cheers & fly Safe. .Hone
Also gotten the impression the Manufacturers have a clue as to how best operate the plant to best effect.
Hey by the way Nick I've just read the S92 checkflight (for about the 4th time) again recently. Love the bit where the chase van gets pushed into the ditch. Are you really that slender and sleek or was it the camera angle??????. .lol
Cheers & fly Safe. .Hone
I decided, why not ask those who know, so I emailed engineering at RHC. Gas_producer was spot on. Here's the note I received back:
"Hate to disappoint you but the answer is a lot simpler than your theories.. .The reason the pre-takeoff check was reduced to 75% was purely to reduce. .noise levels and be neighborly.. .Regards,. .Kurt Robinson"
Guess that means that if there aren't any nearby people to offend, Vorticey could keep doing mag checks at 104% afterall. <img src="smile.gif" border="0">
"Hate to disappoint you but the answer is a lot simpler than your theories.. .The reason the pre-takeoff check was reduced to 75% was purely to reduce. .noise levels and be neighborly.. .Regards,. .Kurt Robinson"
Guess that means that if there aren't any nearby people to offend, Vorticey could keep doing mag checks at 104% afterall. <img src="smile.gif" border="0">
Iconoclast
Join Date: Sep 2000
Location: The home of Dudley Dooright-Where the lead dog is the only one that gets a change of scenery.
Posts: 2,132
Likes: 0
Received 0 Likes
on
0 Posts
A must read for Robie drivers
This should be required reading for all Robinson drivers and students.
<a href="http://www.ntsb.gov/Publictn/1996/SIR9603.pdf" target="_blank">http://www.ntsb.gov/Publictn/1996/SIR9603.pdf</a>
[ 06 February 2002: Message edited by: Lu Zuckerman ]</p>
<a href="http://www.ntsb.gov/Publictn/1996/SIR9603.pdf" target="_blank">http://www.ntsb.gov/Publictn/1996/SIR9603.pdf</a>
[ 06 February 2002: Message edited by: Lu Zuckerman ]</p>
Join Date: Jun 2001
Location: Australia
Posts: 251
Likes: 0
Received 0 Likes
on
0 Posts
these accidents sound like pushover low"g" accidents to me. only one was done in a comercial op, other than instruction. its hard to learn to fly one, but i'd definately fly a 22 before a 47.. .i find a 47 harder to hover than a robbie, the power assistance and throttle are the trouble i think.
Join Date: May 2001
Location: London
Posts: 528
Likes: 0
Received 0 Likes
on
0 Posts
That report has been around for seven years. Do you have a particular motivation in posting it now?. .It states quite clearly that efforts by RHC and the FAA to increase pilot awareness had had the desired effect, and that no design fault was apparent in the helicopter.. .It also, incidentally, pours a good deal of cold water on the Georgia Tech mathematical model that you keep wittering on about.. .Face it, Lu, you're on a loser.
Iconoclast
Join Date: Sep 2000
Location: The home of Dudley Dooright-Where the lead dog is the only one that gets a change of scenery.
Posts: 2,132
Likes: 0
Received 0 Likes
on
0 Posts
To: T'aint Natural
What you say about the report being around for a long time and the actions taken by the FAA and Robinson is true. However, since that report was generated there have been at least seven rotor loss incidents and at least five of them in the last two years with two occurring in the UK. The FAA and Robinson still do not know what caused it so by inference, it was pilot error. I am trying to get an acquaintance to come on this forum and if he does, he can lay it all out so that everyone can understand exactly what happens and why it happens.
What you say about the report being around for a long time and the actions taken by the FAA and Robinson is true. However, since that report was generated there have been at least seven rotor loss incidents and at least five of them in the last two years with two occurring in the UK. The FAA and Robinson still do not know what caused it so by inference, it was pilot error. I am trying to get an acquaintance to come on this forum and if he does, he can lay it all out so that everyone can understand exactly what happens and why it happens.
Join Date: Jan 2002
Location: northampton
Posts: 25
Likes: 0
Received 0 Likes
on
0 Posts
T'AINT NATURAL
The report might have been around for seven years, but how many people have started flying during the last seven years that havn't seen this report?? Surely if any of these more recent pilots have ready access to this information and can learn just one fact it might one day save their lives!!!. .Any way do you have a reason to keep it coverd up?
The report might have been around for seven years, but how many people have started flying during the last seven years that havn't seen this report?? Surely if any of these more recent pilots have ready access to this information and can learn just one fact it might one day save their lives!!!. .Any way do you have a reason to keep it coverd up?
Join Date: Jun 1999
Location: by the seaside
Posts: 216
Likes: 0
Received 0 Likes
on
0 Posts
HALF A PILOT
Maybe you do not realize that Lu does not bring this to your attention to help you learn and enjoy but rather to boost his cause that the Robinson aircraft is a dangerous aircraft and should not be flying.
I don't think that t'aint natural has anything against the information being published only that Lu didn't trumpet it as new information against the Robinson.
Information contained within this document is covered within your helicopter training and if you ask your instructor he should be only too happy to discuss this with you.
[ 09 February 2002: Message edited by: Rotorbike ]</p>
Maybe you do not realize that Lu does not bring this to your attention to help you learn and enjoy but rather to boost his cause that the Robinson aircraft is a dangerous aircraft and should not be flying.
I don't think that t'aint natural has anything against the information being published only that Lu didn't trumpet it as new information against the Robinson.
Information contained within this document is covered within your helicopter training and if you ask your instructor he should be only too happy to discuss this with you.
[ 09 February 2002: Message edited by: Rotorbike ]</p>
Join Date: May 2001
Location: London
Posts: 528
Likes: 0
Received 0 Likes
on
0 Posts
The report is not secret, never has been, and if you read it in full you'll find that it casts no aspersions on the Robinson at all. A deft misrepresentation of it, however, larded with selective and out-of-context phrases, can be used to fuel the obsessions of those to whose bait I should not rise.. .Robinsons now comprise half the fleet and do more than half the hours. They have fewer than half the accidents and far fewer than half the fatalities, despite the uses to which they are put and the lack of experience of the majority of their pilots.. .Damn, I promised myself I wouldn't get involved in this...
Join Date: Nov 2000
Location: Vancouver, BC, Canada
Posts: 452
Likes: 0
Received 0 Likes
on
0 Posts
Dynamics ~ The opposite of Robinson
It has been said that the Robinson has an additional pair of hinges in the rotor hub so that the rotor assembly will weigh less. This has caused some to question the amount of control that is available.. .. .As an idea for consideration, what about the opposite. Give the teetering rotor an amount of rigidity?. .. .What about a teetering rotor hub that is conventional Bell, except that it has a 'spring' device at the teetering hinge. This device attempts to return the rotor disk to its mean position (normal to the mast) when the disk is tipped. This centering device can only impart a small amount of force, but it may result in;. .. .Pros: </font><ol type="1">[*]<font size="2" face="Verdana, Arial, Helvetica"> Faster responses by the helicopter to cyclic inputs. </font></li>[*]<font size="2" face="Verdana, Arial, Helvetica"> A reduced tendency for blade incursion into the tail boom, when the rotor-disk is unloaded. </font></li>[*]<font size="2" face="Verdana, Arial, Helvetica"> No need for droop stops. . .</font></li>[/list=a]<font size="2" face="Verdana, Arial, Helvetica">Cons: </font><ol type="1">[*]<font size="2" face="Verdana, Arial, Helvetica"> The blades, hub, feathering bearings and mast must be slightly stronger and heavier.. .</font></li>[/list=a]<font size="2" face="Verdana, Arial, Helvetica"><img border="0" title="" alt="[Eek!]" src="eek.gif" /> Posted to RAR as well, to see where the 'technicos' reside. <img border="0" title="" alt="[Wink]" src="wink.gif" />