P-47: bad at boom and zoom?

[Rache-der-Boote]

On 6/8/2020 at 2:57 PM, Tomsk said:

 

So here are some data points I just collected in the sim to compare high speed handling. The test was quite simple:

• Start at 9000 ft.
• Go full power, dive down (about 30 degrees) until we reach 400 mph. This generally happens around 5000ft.
• Then roll 90 degrees to the right (timer starts when roll is finished).
• Pull as hard as possible in a level turn (no altitude change), without stalling the plane or blacking out.
• Complete a 360 circle, this is estimated using an easily visible landmark.
• Timer stops when 360 circle is complete, measure finishing speed and time.
   

All speeds and times measured using tacview. Three separate runs were taken for each plane (R1, R2 & R3) and averages made. 

• Start time: time when the 360 circle started, as shown in tacview.
• Start CAS: speed (in CAS) when the 360 circle started, as shown in tacview.
• End Time: time when the 360 circle was finished, as shown in tacview.
• End CAS: speed (in CAS) when the 360 circle was finished, as show in tacview.
• Time (s): the time to complete the 360 circle, end time - start time.
• Delta Speed: the speed loss doing the 360 circle, end CAS - start CAS.

=== P-51 ====================

Full power, 50% fuel.

        Start time  Start CAS (mph)     End Time        End CAS (mph)   Time (s)    Delta Speed (mph)
R1:     0:05        412                 0:19            270             14          142
R2:     0:29        413                 0:45            267             16          146
R3:     0:35        412                 0:50            283             15          129 

Average:                                                                15          139

NOTES: P-51 is G limited here, easy to blackout at any point all the way round.


=== P-47 ====================

Full power, 50% fuel, cowl flaps closed.

        Start time  Start CAS (mph)     End Time        End CAS (mph)   Time (s)    Delta Speed (mph)
R1:     0:33        408                 0:51            231             18          177
R2:     0:00        409                 0:17            221             17          188
R3:     0:06        417                 0:23            233             17          184

Average:                                                                17.3        183

NOTES: P-47 can't pull enough G to blackout at this speed, P-47 also loses so much speed that it stalls before completing the turn.

=== P-38 ====================

Full power, 50% fuel, cowl flaps closed.

        Start time  Start CAS (mph)     End Time        End CAS (mph)   Time (s)    Delta Speed (mph)
R1:     0:28        412                 0:43            251             15          161
R2:     0:35        411                 0:50            255             15          156
R3:     0:25        408                 0:41            247             16          161

Average:                                                                15          159.3

NOTES: P-38 is G limited, it can easily reach blackout.

=== Spitfire Mk IX ==========

Full power, 50% fuel.

        Start time  Start CAS (mph)     End Time        End CAS (mph)   Time (s)    Delta Speed (mph)
R1:     0:29        406                 0:46            271             17          135
R2:     0:30        406                 0:48            285             18          121
R3:     0:27        413                 0:45            295             18          118

Average:                                                                17.6        125

NOTES: very very easy to blackout here, have to be very gentle with the stick and ride the blackout.


=== Bf 109 G-14 ==========

Full power, 50% fuel.

        Start time  Start CAS (mph)     End Time        End CAS (mph)   Time (s)    Delta Speed (mph)
R1:     0:23        407                 0:41            285             18          122
R2:     0:23        404                 0:39            280             16          124
R3:     0:29        409                 0:45            281             16          128

Average:                                                                16.7        124.7

NOTES: more elevator limited than G limited.

=== Bf 110 G-2 ==========

Full power, 50% fuel.

        Start time  Start CAS (mph)     End Time        End CAS (mph)   Time (s)    Delta Speed (mph)
R1:     0:02        402                 0:23            281             21          121
R2:     0:33        403                 0:53            281             20          122
R3:     0:31        403                 0:51            291             20          111

Average:                                                                20.3        118

NOTES: strongly elevator limited rather than G limited.

Conclusions:

•  The P-51 and P-47 both have G suits (other planes do not) which increases the G tollerance for the plane. However, the P-47 cannot pull enough G to blackout at this speed meaning it is elevator limited and cannot make use of the G suit. As a result the P-47 turns no better than the other planes. This supports my observation the P-47 is not handling well at high-speed, it cannot pull enough G to reach the blackout limit at 400mph, unlike the P-51 (or even the Spitfire) which easily can. This is not in keeping with the many reports of the P-47 having strong and responsive controls at high speed.
   
• The P-47 has much much larger energy loss than all the other planes, even though it is turning no quicker. This strongly supports my original observation: the P-47 bleeds energy much worse than every other plane even though it is turning no quicker and pulling no more G. It is the only plane tested to lose so much speed that it tends to stall during the last part of the turn.
   
• The data for the P-38 is included. The P-38 is easily able to reach the blackout limit and completes the circle in the same time as the P-51 (G limited). However, despite the P-38 being heavier and larger than the P-47, and pulling significantly more G than it, it loses less airspeed than the P-47. 
   
• The Spitfire is strongly overperforming: it can easily pull more than enough G to quickly black out, far more than any other plane. This is despite the Spitfire being well known for having heavy and unresponsive controls at very high speeds. The 109 in comparison (a plane that is structurally similar) is elevator limited: you cannot pull enough G to blackout in the 109 at this speed.

What an incredibly thoughtful and well-written post!