View Full Version : Who knows the VAR crank AD date?

Ernie Martin
05-17-02, 09:04 AM
Presumably, engines overhauled after that date MUST have a VAR crank, so I'm trying to find the AD date (the AD number would also tell me).


Bob Cook
05-17-02, 10:39 AM
I will see if I cannot find it. go to www.tcm.com. it is on their site. also do a search for ad's under the faa.

summary; the crank needs to be changed if the case is split or the engine requires overhaul. There were problems with some of the new VAR cranks as well and they had to be tested and/or replaced. About 97 if I remember correctly.

new crank is about 6k. (another way to make money as GMAS says there is no proof the old cranks were bad to start with).

Also need to check the cases. They made heavier crankcases and had an "H" stamped on the side. The earlier or lighter cases were prone to cracking.



05-17-02, 11:59 AM

Yep...Yep... it was actually 96 that the crank AD was first proposed and went into effect in 97... AD 97-26-17... Which states that you have to remove and replace it when ever the crankcases are split.... their are a lot of NON VAR cranks still runing around out their... and then NEW VAR Cranks are not any better...

I once tried to get the FAA to evaluate the new cranks under the old guidelines... to show that the new VARS are not as good... nothing doing.. they headed me off at the pass... because they know that the new ones are more probamatic than the older ones...

With that said... I have to make one point here... and that is.. IF YOU ARE USING A TURBO engine... you need the VAR crank... why.. because those engines don't get a break on the HP that is produced... while the normal asprated engines start decreasing power once your above 5000 feet...

Its the springing of the crank and the counter weight and pins that we are most conserened about... which is the balance of the crankshaft to the prop in rotary motion... (big engineering turm)... and that is why we suggest that you never run the 360 below 2300 RPM... as it keeps all the springiee stuff from springing... and the banging stuff... from slapping back and forth... (counter weights on the crankshaft)

If you noticed at the meeting I covered the "PROP BALANCING GUYS"... it is here that most pilots and mechanics don't really understand what is going on inside the engine with the counterweights... and balance... so basicly to save room and bordome... it is summed up... don't do it... if you have a prop that you think is out of balance.. take it off and take it to the prop shop.. their they will balance it... if you get lots of vibration... your engine is trying to tell you something... (see the part about your engine really does talk to you... but, sometimes the owners just don't listen)....

the counter weights and the 1,2,3,5,6 being the biggies harmonics... of the crankshaft are the killers.... and if one is interested in that subject... their are lots of different views on the subject written...

Hope that this helps.. G.M>