Helosammy,
If I'm not making too many assumptions from your hints of your location, why not make contact with some of the retired Canadian military pilots who have been operating the S92 commercially in your locale for years.
Your definitions above are roughly correct, but you're definitely confusing your thoughts by including what you call stay-up at OEI MCP in a discussion about take off calls. OEI MCP at a certain altitude, allows you to calculate the stay-up weight at that altitude. So, a primary example of its use would be calculating your maximum weight at a minimum IFR cruising altitude. The only relation it has to take off performance, is that a limitation on cruising altitude weight, may also dictate that you need to take off at a low weight to achieve what's required at altitude.
Vtoss is as your definition, it's the speed that will guarantee you a 100fpm climb with the gear down. That is, it's the speed that will get you climbing clear of runway environment obstacles. That's why it only needs to be for 2 mins.
Vy, we all know. It's defined as being at MCP in formal take off performance planning, because it needs to get you to 1000ft above the take off surface and that will take several minutes at the defined 150fpm.
(BTW, if you really want to amuse/ frighten yourself some day, think about the horizontal distances you will travel, if you are climbing at the minimum guaranteed rate of climb in the Vtoss and VY sectors. It works out in the order of 2 miles to get you to 200ft and a further 7 or so, to get you to 1000ft. It sort of emphasizes nicely that this performance planning is for a runway environment)
What you're calling safe- single 30secs, aligns with what full blown commercial ops call Vtdp. That will define a airspeed, AT A CERTAIN TAKE OFF WEIGHT, at which you can accelerate towards Vtoss and then start aviating as your god and squadron commander planned you to. For your military ops, being aware of formal Vtdps and associated take off weights is going to give you a good " guess" at which point to call fly-away. If you call too early at a high weight you're not going to have the performance to accelerate and achieve Vtoss.
True commercial operations not only take the ability to fly away into account, but also the ability to stop on the runway surface ahead, if a engine is lost before Vtdp. The S92 RFM is a bit weak on that calculation, effectively you have to use your TO weight to calculate Vtdp, the combination of which gives you the runway length required for take off. Of course that's all a bit backwards to the real world, so what you end up doing is several circular calculations to give you a take off weight that relates to your actual runway length.
In simple terms. For high weight you need a higher Vtdp and hence Vtoss before the thing will fly. But that high Vtdp may not allow you to stop on the runway remaining, so in that case you would have to reduce your weight to lower your Vtdp.
Last edited by inputshaft; 11th June 2014 at 02:24.