yellow arc on AA5B

[andrew_wallis]

Hi Chaps

Im the proud 1/3rd owner of an AA5B-180 Tiger. On the Rev counter theres a yellow arc between c1850 and 2250 rpm, which relates to a problem with vibration during descending flight.
Research elsewhere suggests its to do with the original prop/engine combination- a Mcauley prop originally.
The plane has had the prop changed for the Sensitech one, the engine remains as original. I gather this is a common upgrade as there were problems with the original prop in the AA5B installation.
Am I correct in thinking the yellow arc can now be disregarded?

TIA

[Pilot DAR]

Strickly speaking, no, you cannot disregard a placard or marking, unless there is another one, placed in accordance with an approved (by STC usually) installation, which changes/cancels it.

That said, what you say makes some sense, and is worth a follow through. Do the following:

Find the approval document, either on the Type Certificate Data Sheet (TCDS) for the aircraft, or the propeller, or an STC for the installation, and review them carefully. If there is a limitation, which would certainly include a yellow range marking, it will be stated there, or in a referenced document (but really should be on the certificate). The referenced document would generally be a flight manual supplement, which if it extists, you sure should have!

If there is no changed limitation, the yellow range marking still applies. If there no longer is a limitation, or it is different, there will be something which restates that situation.

If you have trouble finding the TCDS for the aircraft or the prop, tell me the exact prop model, and I'll find it for you. If it is an STC, it's not so easy, unless you have the number. You maintainer should be able to find that for you from the aircraft records.

Congratulations on ownership, enjoy the freedom!

[englishal]

Check the STC for the new prop. We had a limitation with the old 2 blade - "Avoid continuous flight below 20" MP". With the new 3 blade, this drops to 15" MP.