''Safety'' procedures
I know I usually don't usually initiate threads, but this one issue has been bothering me lately. In the "Priceless Tips" thread, one of the posters makes the suggestion of putting the blades of a two-blade helicopter at 90 degrees prior to starting. This has become a sort-of-accepted and fairly widespread practice that is done in the interest of "safety", of course. The theory being that you cannot start the ship with the MR blade tiedown on if the blade is at 90 degrees.
Hmm.
I laugh often, but never so heartily as when I see a well-meaning 206 pilot (especially a 206L pilot) who conscientiously pulls his main rotor blades out to 90 degrees, and then leaves the tiedown on the blade! instead of stowing it. Now there's a classic set-up.
There's something else. I don't know about your AFM, but mine says that the main rotor *must* be turning by 25% N1. If not, you have a problem that must be investigated. For pilots who put their blades at 90 degrees, I wonder how they verify that the MR blades (i.e. the N2 turbine) is turning by 25% N1? I guess my bigger question is: Why do some pilots feel that they can ignore a fairly important checklist item in the name of convenience?
This is not a silly or inconsequential point. I used to fly one particular ship regularly. I took a couple of days off, and a pilot filled in for me. When I got back, on my first start the blade didn't even begin to turn until 30% N1. I shut down and walked the blade around and around backward in a futile attempt to "free-up" the lab seals on the N2 turbine wheels. We ended up changing the turbine because the fill-in pilot was "short-cooling" the engine. I never would have known this if I was in the habit of parking the blades crossways prior to the start. Silly, dangerous me.
Yes, yes, you'll probably discover any binding of the N2 if you pull the blade backward as you untie, but the dang ol' 206B has a MR tiedown setup that leads you into moving the blade in the direction of rotation during the untying process.
To my way of "thinking," it is better to glance up at the blade for a moment during the start to verify that it is indeed turning by the proper rpm. In this way, you verify two checklist items: 1) that your N2 is not locking up, and 2) that you've untied the main rotor. Focusing too intently on the TOT gauge is not healthy. There's a lot going on during the start, and you cannot become tunnel-visioned.
Our three and four-blade aircraft all use at least one tiedown on the main rotor blades. So on an AS-350, say, seeing no blade above you is no guarantee that the tiedowns are off. Similar with a BO105.
I believe that the "blades at 90 degrees" crowd are misguided, and that they've come up with the wrong solution to the problem of leaving the main rotor tiedown on.
Your thoughts?