Stability and Control characteristics of the Early Mark Spitfires

[IvanK]

Not special training just authorisation.

Issue Date July 1940 Revised Dec 1941 and Amended up to Al No 25K which was added according to the AL sign off sheet as Aug 1942.

[Crumpp]

Aug 1942

Ok, that is after the inertial elevator was added to the design.

[IvanK]

Inertial elevator ??

Are you referring to the bob weight in the pitch circuit or increased balance area on the elevator as fitted to MKV's ???

[DC338]

Can I ask for your analysis of figure 16 17 & 18 of the NACA report? It seems figure 15 was an anomaly when compared to the next 3 which where doing similar test?

Someone (whiny?) earlier quoted a report from the morgan book on the Spitfire about inertia weights being not required for the MK I & II as long as the rear oxygen bottle was removed. Would be interesting to see the full report.

[MiG-3U]

IvanK,
The early version of the Mk II manual, which Crumpp is quoting, is for the planes with Rotol props only before the CoG limits were revised. Later the planes (any early Spitfire) with the Rotol props got tighter aft limits, 7.5" aft datum with atandard elevator and without bob weight, while the planes with the DeHavilland prop only got limitations for extended CoG limits, bob weigh required if CoG 7.9" aft datum. In other words bob weigh was not required for the planes with DeHavilland propeller.

The later manual you are quoting is for the Mk IIs with both propellers, Rotol and DeHavilland, after the CoG limits were revised, hence no warnings about the elevator control reversal. Note that longitudal instability and elevator control reversal are related to each other and CoG but not the same thing.

As pointed out earlier with documentation and calculations, the NACA tested Spitfire had the CoG at 7.8" aft CoG and Rotol prop, in other words the CoG was behind the limits and the results are not representative for all the early Spitfires nor all CoG positions.

[IvanK]

I think the Oxy bottle statement is discussed on P143 of the Morgan Shacklady book.

Here is the bit.



The 30 June meeting discussing the general fitting of bob weights refers only to the MKV.

The Bob weight was initially trailed on the one off Spit MKIII. It was tested also on a single MKII airframe P7280 that features in a lot of the RAE tests.
So unless more evidence is provided there is nothing to confirm that bob weights were actually fitted to operational MKII's

Spin trials by RAE on the MKII and MKI (as posted earlier in this thread) generally considered spin characteristics as normal ... no real drama.

Here they are again !









Thanks Mig-3U more evidence that operational Spit II's wernt fitted with Bob weights.