oriol
Well-Known Member
Hi all!
Since a few days back, I have been wondering about using a motorglider not only for fun but for commercial transport too, that is carrying loads/passengers.
If the energetic/economic cost of the flight done by the motorglider would be less than with a conventional air cargo. The cargo motorglider would be an interesting and competitive option against traditional cargo/airliners. I´m considering medium regional range flights about 400/500 Km, maximum 1000 Km.
Even though gliding is independent from mass, cargo sailplanes are very rare.
Most of them date back from WWII: british general aircraft Hamilcar, german Me 321 (powered) and Junkers 322 (only two prototypes were built of this very modern looking airplane). Many countries developed military cargo gliders during the period time.
List of World War II military gliders - Wikipedia, the free encyclopedia
The basic idea is to benefit from the gliding coeficient, in order to fly unpowered as much as possible during the flight. This would involve flying in little hops: climbing powered periods of the fligh interpersed with gliding periods.
One of the big points is that instead of flying form thermal to thermal, wich excludes to fly straight from A to B, the pilot would only use the engine to attain a certain altitude. Once the altitude is reached he would cut off the engine and starts gliding to repeat the cycle (climbing->gliding->climbing->...) as many times as needed in order to get to its final destination.
The following (very silly) example works as a first aproach, of course I use estimative values to solve the equations.
Empty weight 5000 Kg,
Maximum loaded weight 15000 Kg,
Gliding coefficient about 20/1
Distance 400 Km
Gliding speed 300 Km/h (83,33 m/s)
-)If I consider the distance traveled during the climbing periods to be negligible and considering the gliding speed to be constant.
The total time of the flight is 80 minutes.
-)If the altitude reached for a climbing period is of 2Km, for each climb I would glide 2Km*20 = 40 Km.
Then I would need to start my engines (400/40 =) 10 times during the flight.
-)Surface area:
*)I consider Cl = 0,5, p = sea level, V = gliding speed, W*times a safecty factor of 1,5
L=W, I isolate S from L:
S = (1,5*m*2)/(p*V^2*Cl) -> (1,5*15000*2)/(1,225*83,33^2*0,5) = 900000 / 8506,26 = 105,84 m2
The air tractor is somehow similar in cruise speed and both empty/Gross weight are half those of the cargo glider. So eye guessing it would require a twin airtractor engine (PT6) about 3000 HP total power.
Legal issues:
Maybe traffic controlers would oblige you to fly under a certain altitude in order to avoid the motorglider to interfere with airliners flying at constant altitude.
If this would be the case the pilot would be forced to perform severol hops in order to cover the distance.
If the airplane is considered a motorglider you won´t be forced to follow prefixed airways, you could fly straight form A to B and perform the minimum required hops/ climbing periods: no maximum altitude imposed.
Technical considerations:
About the powerplant, I don´t know if flying by hops and therefore using the engine intermetently would imply many inconvenients: engine preheating prior to start and others.
Maybe the engine should be runing to idle during the gliding, that will increase safety and gas consumption aswell.
Business perspective:
My personal view is that, albeit an unothodox plane, there is a possibility that the machine will have a niche in the existent market, particularly the charter/low cost market. The tickets would have competitive prices!
Plus the ecofriendly factor gives some commercial knack. The companies using this motorglider would be clearly distinguishable from the rest.
do you think the idea makes sense?
thanks,
Oriol
Since a few days back, I have been wondering about using a motorglider not only for fun but for commercial transport too, that is carrying loads/passengers.
If the energetic/economic cost of the flight done by the motorglider would be less than with a conventional air cargo. The cargo motorglider would be an interesting and competitive option against traditional cargo/airliners. I´m considering medium regional range flights about 400/500 Km, maximum 1000 Km.
Even though gliding is independent from mass, cargo sailplanes are very rare.
Most of them date back from WWII: british general aircraft Hamilcar, german Me 321 (powered) and Junkers 322 (only two prototypes were built of this very modern looking airplane). Many countries developed military cargo gliders during the period time.
List of World War II military gliders - Wikipedia, the free encyclopedia
The basic idea is to benefit from the gliding coeficient, in order to fly unpowered as much as possible during the flight. This would involve flying in little hops: climbing powered periods of the fligh interpersed with gliding periods.
One of the big points is that instead of flying form thermal to thermal, wich excludes to fly straight from A to B, the pilot would only use the engine to attain a certain altitude. Once the altitude is reached he would cut off the engine and starts gliding to repeat the cycle (climbing->gliding->climbing->...) as many times as needed in order to get to its final destination.
The following (very silly) example works as a first aproach, of course I use estimative values to solve the equations.
Empty weight 5000 Kg,
Maximum loaded weight 15000 Kg,
Gliding coefficient about 20/1
Distance 400 Km
Gliding speed 300 Km/h (83,33 m/s)
-)If I consider the distance traveled during the climbing periods to be negligible and considering the gliding speed to be constant.
The total time of the flight is 80 minutes.
-)If the altitude reached for a climbing period is of 2Km, for each climb I would glide 2Km*20 = 40 Km.
Then I would need to start my engines (400/40 =) 10 times during the flight.
-)Surface area:
*)I consider Cl = 0,5, p = sea level, V = gliding speed, W*times a safecty factor of 1,5
L=W, I isolate S from L:
S = (1,5*m*2)/(p*V^2*Cl) -> (1,5*15000*2)/(1,225*83,33^2*0,5) = 900000 / 8506,26 = 105,84 m2
The air tractor is somehow similar in cruise speed and both empty/Gross weight are half those of the cargo glider. So eye guessing it would require a twin airtractor engine (PT6) about 3000 HP total power.
Legal issues:
Maybe traffic controlers would oblige you to fly under a certain altitude in order to avoid the motorglider to interfere with airliners flying at constant altitude.
If this would be the case the pilot would be forced to perform severol hops in order to cover the distance.
If the airplane is considered a motorglider you won´t be forced to follow prefixed airways, you could fly straight form A to B and perform the minimum required hops/ climbing periods: no maximum altitude imposed.
Technical considerations:
About the powerplant, I don´t know if flying by hops and therefore using the engine intermetently would imply many inconvenients: engine preheating prior to start and others.
Maybe the engine should be runing to idle during the gliding, that will increase safety and gas consumption aswell.
Business perspective:
My personal view is that, albeit an unothodox plane, there is a possibility that the machine will have a niche in the existent market, particularly the charter/low cost market. The tickets would have competitive prices!
Plus the ecofriendly factor gives some commercial knack. The companies using this motorglider would be clearly distinguishable from the rest.
do you think the idea makes sense?
thanks,
Oriol
