Jump to content

Notice: Effective July 1, 2024, Vertical Forums will be officially shut down. As a result, all forum activity will be permanently removed. We understand that this news may come as a disappointment, but we would like to thank everyone for being a part of our community for so many years.

If you are interested in taking over this Forum, please contact us prior to July 1.

Chopper Crash Terrace, Bc

Recommended Posts

  • Replies 70
  • Created
  • Last Reply

Top Posters In This Topic

Please feel free to split this off into it's own topic if you desire Mr Moderator.


Just to relight the flame so to speak on M/R and T/R strikes and their relationship to one another, I was leafing through a manual (manufacturer shall remain anonymous) and noticed that the two special inspections are kept separate from one another. You have a M/R strike inspection and a T/R strike inspection. Nowhere does it state when you have one you must do the the other. I assume this is due to the fact that a strike is a strike, such as hitting a tree etc. Once you end up in a situation where there is an accident, I personally do not believe that those special inspections apply anymore, nor can you look at them in a separate light so to speak. The manufacturer should be consulted in any accident, no matter what the book says. Let them make the call and accept ultimate liability.

There is some inspection criteria that will help you determine how far you must go with an inspection/repair/overhaul of a component and that is clearly stated and should not create any confusion. Damage found on weaker links in the system such as shafts, couplings etc are a good indicator of the extent of sudden stoppage experienced.

A fine example of how far you should go when an aircraft rolls on its side opposite the T/R and the T/R does not impact anything. Would you do an overhaul on the gearbox? According to the T/R strike criteria, it never hit anything, and unless your shafting/coupling etc shows damage (which are the weak points) would you O/H the TRGB? Not according to the books you wouldn't need to. But wouldn't you at least like to ask someone who has more knowledge and experience?

It's obvious to me a T/R in that scenario went through a rapid decelleration, but not as rapid as hitting an object. There are other factors at play, such as power on VS power off, that can greatly change the outlook, and all those need to be looked at.

I'm not familair with the innerds of a 500 TRGB, so I do not know how well they accept abuse. With their fairly beefy size TRDS and Kflex couplings direct driven off the MRGB, there is a good chance that a sudden stoppage on the M/R is far more detrimental to a T/R system than other models.

Link to comment
Share on other sites

PerfectTrack: I don't know if you are an AME, but once the helicopter rolled on it's side under power, the whole drive system was shock loaded. I personally don't need a MM to tell me what needs overhauling.


If you are not using the manual of CDF (common dog f**k) it's also called common sence.


If you have a licence and don't understand shock loading, what can I say.



Link to comment
Share on other sites

It's very hard to express all my ideas in such a short space and time frame, but had you closely read my post you would have read that I know and understand what shock loading is. I quote myself for your ease "It's obvious to me a T/R in that scenario went through a rapid decelleration, but not as rapid as hitting an object" and "I personally do not believe that those special inspections apply anymore". I myself in the performance of my duties would not hesitate to send the T/R gearbox for overhaul, but when you get some deadheads who take the book word for word, you can't do much.

When I talk about driven or not driven you'd have to be looking at excactly what I mean to understand. A 500 for instance does not have an engine between the two gearboxes. Imagine a 206 or A-star for that matter with the powerplant in the middle, stop one side completely, can you honestly tell me that the other end stopped at the same rate? No, simply because all the shafts, couplings etc in the middle absorbed some of the impact, and with the engine still producing power some of those parts likley failed as a result, ending the potential "sudden stop" on the other side immediately or not even getting there at all. The 500 is similiar, yet it's more obvious that the "sudden stop" would not be isolated as much from the other end because there is not as much between them to absorb the impact and the T/r is not directly driven from the engine. I wish I had a basic table top version so I could prove my point to you.


Every one of those "weak links" in the system acts as a shock absorber reducing shock loading, so no wonder you check the twist of a 500 shaft after a T/R strike (it's a perfect indicator). Too bad many of the bendix couplings, which would shear immediately, have been replaced by a more rugged and sturdier K-flex coupling. And feel free to argue that all you want, you're entitled to your opinion.

Link to comment
Share on other sites


Out of darkness, a ray of light! How awesome is that?! What a wonderful reason to continue to fight. Congratulations to Mr. Phil and mommy. Godspeed in healing!

Link to comment
Share on other sites

  • 12 years later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...