I had the 75 with the better cowl and small tail and my speed was never what the book claimed. Also, the speed specs were quoted at some real high RPM that was beyond any 75% I could think of(despite reduced MP).
So, I checked my fairings, made sure it was rigged right(flew straight and hands off), clean inside, baffles good and tach basically correct. It was just not making what I thought the book claimed of 128 kts. I could get about 115 kts or so but that was it, no matter what I did.
I think the factory cooked the books a bit on the AA5 series, and they are actually pretty much in line with the same power 172. While they might be a bit more slippery than the Cessna, the squared off boxy fuselage and rather fat wing give it a rather limited top end.
100kts does sound low, for a 74 model, but if the engine is tired, and the prop has been filed on a lot, and the ailerons may be drooping a bit, I guess it's possible. The only thing I found on my plane was the fairings were all deformed a bit. The gear leg fairings and the wing tip fairings had waves in them that made them stand proud of the rest of the structure a bit, and that had to knock off some speed. The cost to replace all those was up there so I just cleaned them and lived with it. Once I had a chance to swap it for a Bo, I grabbed it and never looked back. I can do the same speed and fuel burn on the Bo, and carry more, or turn up the wick and do about 180MPH if I want to buy a lot of gas.
The AA5 is a great flyer, but it's not the speed demon I was hoping for on 150HP.
