Vdd test complete.

[ChiefPilot]

I posted a while back about Vne testing; I thought I'd post a follow-up note to that now that I've completed that portion of my phase one testing.

After consulting a number of folks smarter than I, I made the decision several months ago that my phase one testing would include include a test to design dive speed. In traditional aircraft, Vne was determined to be 90% of this value, and given the relatively close proximity of cruise and Vne in these aircraft I decided that doing this test would be a good idea as there exists a possibility that an upset at high cruise might broach Vne anyway.

I did several things in the way of preparation for this test. I was prepared and equipped mentally and physically to escape the airplane should that be needed; this means a chute, helmet, and practicing getting out from underneath the jettisonable canopy. Another prep item which was critical was another test card: I needed to know the accuracy of my airspeed indicator and establish a correction factor to be able to convert from IAS to CAS. Finally, smooth air and sufficient ceilings were required so I waited for this test until a day with appropriate weather.

The Vdd test card started at 10,000ft MSL (~9000 AGL) and included a series of progressively steeped descents at maximum power. The first descent peaked at 160KTAS, where I exercised yaw/pitch/roll response then let the aircraft fly "hands off" for five seconds. I followed this procedure again at 170KTAS, 175KTAS, 180KTAS, and 182KTAS. This took my plane (RV-6A) up to it's published Vne value.

I had previously computed Vdd as 202 KTAS (182/0.9). Using the above procedure, I reran the profile at 185 KTAS, 190 KTAS, 195 KTAS, 198 KTAS, and 202 KTAS.

What did I learn from this test? Two things:
1. The plane exhibited no bad characteristics at Vne.
2. There is a small margin, in smooth air, beyond Vne. This belongs to Van, not me, but it does exist.

What did I gain? The actual knowledge that I can operate up to Vne in smooth air, and that if I do so with a friend of family member on board, they won't unknowingly be a test pilot. That alone made the Vdd test card worth while.