Jet turbine reliability

Op zaterdag 6 juni 2015 21:02:52 UTC+2 schreef jfitch:
For reference, an ASH26E uses about 2 liters for a warm up and climb to 2500 ft agl, and will do 680 Km on its 16 liter tank (according to the book - never had a retrieve that long!). To do that you climb to altitude limits then fold the engine and glide, and repeat as needed. Is the climb performance on a jet significantly better so that the climb and glide technique improves retrieve range over a level cruise?

Yes. The higher the thrust/weight ratio is, the more it pays off. Best CLIMB speed for example for a 450 kg ship and a 800N jet is way above 100 kts.

For highter thrust/weight ratio's, fuel efficiency goes up too; a dolphining flight can get similar mileage to a decent car, even with the typical fuel burn of such a jet (70 kg/hr for the 800N AMT).

I have seen various slightly different graphs from JS for ways of using their jet but consistently they predict the greatest theoretical range being from a full power climb at around 80 knots and then glide.

Next best is the economical cruise at about 75,000 rpm and around 75-80 knots - similar to the HpH scenario but JS haven't included the dolphining effect. All flight traces I have found of the JS1 jet being used for real life retrieves seem to show it being used for slow climb and cruise around 75 knots.

I am not sure if including extra range from dolphining gives a valid comparison as there is no stated model of the amount of dolphin-worthy lift being flown through. Also I would have thought that if there was enough lift to gain significant range from dolphining I would turn off the jet and get proper netto and STF info to dolphin efficiently - bearing in mind that these computations rely on the polar in the computer being the same as the glider which it clearly isn't with any engine running (even without considering prop/jetwash effects on the fin probe).

What range does JS predict when using these techniques?


On Sunday, June 7, 2015 at 3:12:48 AM UTC-7, wrote:

I have seen various slightly different graphs from JS for ways of using their jet but consistently they predict the greatest theoretical range being from a full power climb at around 80 knots and then glide.

Next best is the economical cruise at about 75,000 rpm and around 75-80 knots - similar to the HpH scenario but JS haven't included the dolphining effect. All flight traces I have found of the JS1 jet being used for real life retrieves seem to show it being used for slow climb and cruise around 75 knots.