If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#21
|
|||
|
|||
Bill Daniels wrote:
Straw man argument. Of course you train for premature launch failures - just like you do for airtow. The original drift of this thread seemed to suggest that launch failures were epidemic with winch launch. With a well run winch operation the launch failures won't be any more common than with air tow ... I disagree. I've never seen any winch operation with a failure rate as low as most aerotow. I share your enthusiasm for winches but don't oversell them. ....snip My remark about no launch failures was based on the German Dyneema test group's reply to a question about how they dealt with breaks. Their reply was, "we haven't had any." Exactly. You equated no cable breaks to no launch failures. The discussion was about a field where cable breaks couldn't be practiced. Simulated cable break is how winch operations train their pilots to handle ALL premature terminations of the launch - weak link failure, engine failure, failure of the laying gear, jams in the feed rollers, even the drum falling off because of fatigue cracking of the hub, even sometimes, the Dyneema failing. The reliability of the cable is the straw man in this argument. I don't care if the Dyneema never breaks, if there's no way of practising premature termination of the launch skills and procedures, the field is unsuitable as a base for winching. There was some scepticism expressed that it would be suitable for aerotow if it wasn't suitable for a winch. I think that's a good question but neither of us have seen the field so there's nothing useful we can say on that. Graeme Cant Bill Daniels |
#22
|
|||
|
|||
"Graeme Cant" wrote in message ... Exactly. You equated no cable breaks to no launch failures. The discussion was about a field where cable breaks couldn't be practiced. Simulated cable break is how winch operations train their pilots to handle ALL premature terminations of the launch - weak link failure, engine failure, failure of the laying gear, jams in the feed rollers, even the drum falling off because of fatigue cracking of the hub, even sometimes, the Dyneema failing. OK, I see your point. Launch failures can occur for other reasons than cable break. However, those that you mention can be largely eliminated by good design and mantenance. The most common reason for launch failures I have seen other than cable break is the winch running out of gas. That's pretty easy to deal with. Replacing steel wire with Dyneema/Spectra itself eliminates a lot of failure modes since the stuff really doesn't want to tangle or jam. Reducing the rotating mass of the drum helps too. 5000 feet of 3/16 inch wire rope weighs about 300 pounds. The same amount of Spectra weighs about 50 pounds. The reliability of the cable is the straw man in this argument. I don't care if the Dyneema never breaks, if there's no way of practising premature termination of the launch skills and procedures, the field is unsuitable as a base for winching. Absolutely agree. If you can't practice launch failures, the field is unsuitable. There was some scepticism expressed that it would be suitable for aerotow if it wasn't suitable for a winch. I think that's a good question but neither of us have seen the field so there's nothing useful we can say on that. If a launch failure of air tow or winch would put the pilot at risk, there needs to be some serious thinking about proceedures. Bill Daniels |
Thread Tools | |
Display Modes | |
|
|