I made a series of tests today to figure out Spit14's best glide speed. I took a Spit14 with 50% fuel and used the SW spawn at A22 in the training arena. Prop RPMs were set to minimum.
TEST 1: Used 175mph for the first test (HTC's programed autoclimb speed for Spit14). After landing, I asked someone to serve as a reference point for my further tests. Had him put his airplane right where my is in order to measure distance for further tests.
TEST 2: 200mph, landed 5K before the reference point.
TEST 3: 165mph, landed 3.1K after the reference point.
TEST 4: 140mph, landed 3.3K after the reference point.
TEST 5: 130mph, landed 3.3K after the reference point.
TEST 6: 135mph, landed 3.8K after the reference point.
135 mph is the best glide speed for Spitfire mk XIV is this configuration.
I know in reality the plane will glide further with prop stopped than feathered. So I decided to test if HTC implemented this in AH.
TEST 7: Used the same 135mph as before. With the engine ignition off I had pitch up and reduce my airspeed beyond stall to 20mph which caused the airplane to climb another 2000ft, then since the airplane was already in the stall I had to dive down to initial altitude to recover from the stall. Then I continued the glide. I landed beyond 6K from the reference point so I do not know the exact distance. Since in test 6 I landed 3.8K from the reference point I this test proves that the plane glides better with the prop stopped. Additionally in test 6 I overflew the reference point at 2000ft MSL, in test 7 I overflew the reference point at 4000ft MSL, which additional proves that gliding with prop stopped results in a longer & more efficient climb.
This demonstrates that the energy lost due to maneuvering to get the prop to stop can pay of assuming that the glide is from a relatively high altitude.
Note: It will not necessarily pay off if the glide is from a low altitude.
WARNING: DO NOT DO THIS AT LOW ALTITUDE AS YOU MAY NOT RECOVER FROM THE STALL.
Special thanks to Electric for dedicating his time acting as a reference point.