The requirement is not hit and miss but is a bit complicated to do it accurately and may need more data than what you have ready to hand. I suspect that you will need to meet two requirements. One is take off length with a glider on tow and the other will be minimum climb rate with a glider on tow.
Anyway an attempt to answer the climb question (feel free to correct any errors anyone!) with a simple answer: Climb speed is roughly equal to: Air Speed x ( thrust to weight ratio - 1 / (L on D for that airspeed)) Or: Climb speed = Air Speed x ( thrust at that airspeed - drag for that airspeed) / weight So with a glider on tow the weight is increased and the drag is increased. A bit of an experiment is required if you don't know some bits. The pilots manual should tell you what best climb speed is (this will change slightly with a glider on tow, but not by a big amount?). Fly straight and level at this speed. Note your engine RPM. (This will give you an idea of power for straight and level where thrust = drag). Hopefully the pilots manual will have a power curve per RPM. Now go to max sustainable revs and climb at the same airspeed. Note your climb rate. This gives you a conversion factor where: Climb speed = Factor x Air Speed x ( max sustainable HP - cruise HP for that airspeed) / weight You know how heavy the tug is and how heavy the glider is. You need to make an intelligent guess how much extra drag a glider adds (in horsepower). You can make a good guess by asking another aerotow club to do a straight and level in their tug with and without the glider at the same speed and note the extra horsepower required. So climb speed with glider roughly equals: Factor x airspeed x (max sustainable HP - (cruise HP + glider additional HP) / (tug weight + glider weight) So a more powerfull engine will have higher max HP but will also add some more weight to the tug. Note that I haven't mucked around with prop efficiencies or anything else. The best way of improving a light aircraft as a tug is to fit a prop that is optimised for climb rather than cruise. Hope this helps Anthony > This then leads on to the question, if an aircraft is able > to be fitted with a hook, how does one work out the > engine power requirement? Is it a hit and miss affair? Or > is there a calculation that can be done? > > Cheers- > > Ron. > > _______________________________________________ > Aus-soaring mailing list > [EMAIL PROTECTED] > http://lists.internode.on.net/mailman/listinfo/aus-soaring > _______________________________________________ Aus-soaring mailing list [EMAIL PROTECTED] http://lists.internode.on.net/mailman/listinfo/aus-soaring
