Difference in Vne

W

wpbarnar

New member
Why is there a Vne difference (200 mph versus 180 mph) between Super Decathlons? I always assumed it was a post and pre ACA thing with the metal spar. However I flew a '92 straight Decathlon recently and it had a 180 mph Vne so that assumption does not hold up since this is an ACA metal spar 8KCAB. Was the Vne increased sometime in the mid '90s by ACA and the '92 model just built before change?

Bill
 
From the FAA Type Certificate information:

NOTE 8. The following changes apply to 8KCAB aircraft serial numbers 934-2003 and up and to any other 8KCAB (180 hp.) that has 7-1535 wing frames (or 7-1521 covered wing frames), extended main gear (gear leg part numbers 4-2038, 4-2035, or 4-2139), and the Approved Flight Manual Supplement.

Airspeed Limits (CAS)
Never exceed 200 mph (174 knots)
Maximum Structural Cruising 160 mph (139 knots)
Maneuvering Normal Category 107 mph (93 knots)
Acrobatic Category 130 mph (113 knots)


Maximum Weight 1950 lbs. Normal Category
1800 lbs. Acrobatic Category
 
150 HP = 180 Vne
180+ = 200 Vne
You flew a 92 straight? You know that we only built ONE 150 HP....ever. I would guess that it was a 1992, so that's it.

Fixed pitch, right?
 
Yes, 150 HP fixed pitch S/N 696-92. - Nice airplane

What was the rationale to limit the 150 HP to 180 Vne? Was it just a type certificate thing that was not worth the hassle to change?

Bill
 
I had a nice '79 8KCAB with 150 hp and a fixed pitch prop. It had a fine pitch prop when I bought it and I eventually had it repitched coarser so that renters would be less likely to over-rev the engine.
FAR 23 has a requirement for fixed pitch props and engine max RPM with throttle closed at Vne so that would be the reason for the lower Vne.
 
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