JP5 Strakes
Bit late in on this thread, but the following may be of interest. It comes straight from the gospel's mouth, the Gospel being Reggie Stock, ex Huntings and then BAe cheif test pilot for the Mighty Mouse in its various forms
1. The company had to do lots of work to correct the initially poor JP5 spin handling. Originally, the spin was very oscillatory, with large hesitations in roll, yaw and pitch throughout the spin, including roll reversal and pitch attitudes that varied from past the vertical to above the horizon.
2. Spin recovery from these oscillatory spins varied significantly, from immediate to prolonged – up to 2 turns, which is a long time for a basic training aircraft.
3. The oscillations got worse with reducing ful state. (He noted wryly that even though spin handling was unacceptable at near max fuel, they still completed a full programme down to low fuel weights, just to prove it! When Reggie is being wry, the rest of us would have a coronary)
4. They originally put the large strakes under the rear fuselage, but they made the spin even worse. (An aside from teadriver, rear strakes are the conventional place to put strakes, to reduce AOA in the spin. Just goes to show that spinning's still a black art.))
5. Putting the strakes under the nose cured the adverse handling completely.
6. Reggie reminded me that the primary recovery control in the spin is the rudder, and that it is important to correctly identify the direction of spin and then apply – and maintain – full anti-spin rudder until the rotation stops. Most of the RAF incidents occurred because the pilot did not maintain recovery rudder long enough, or changed rudder because he thought nothing was happening.
7. The JP 3 and 4 spin fine, except when carrying tip tank fuel, and with an asymmetric fuel state – the Pilot’s Notes cover that aspect well.
8. The roughened leading edges are there to improve aileron effectiveness at and during the stall. They have no effect in the spin, when the wing is effectively fully stalled.
9. The roughened walkways have no effect on stall or spin handling nor on drag and performance.
10. The rear fuselage strakes are there to try and reduce the amount of dutch roll (usually seen as snaking, i.e. mainly yaw with little roll) in normal cruising flight. The JP5, with it’s large cockpit and front fuselage area, was worse in this respect than the JP3 and 4. Those strakes have no effect on the spin.