Posted Monday, April 5, 2010 @ 03:46 PM  

Reason being that if you can not get a decent climb rate in climb setting then it will only be worse in the cruise setting
since it will not generate as good thrust when below cruise speed.

Cruise pitch is adventagous once you have good airspeed and have cleared all obsticles and terrain after takeoff.

Taking off in cruise pitch could double or triple your takeoff run distance and result in a poor rate of climb until your airspeed has reached cruise speed.

There are conditions when the cruise setting will allow you to climb a bit better, but its NEVER on takeoff.

Also, in marginal conditions, beware of ground effect. I have seen a guy take off into ground effect only to settle back to the ground after clearing the fence.....although in this case the ground where he settled was a lake, and he made a big splash. Big Bear Lake, CA. The density altitude was 9,500' that day and the Grob 109 got off fine in the 80F weather and made 300 fpm climb.

When I take my Hoffman V62 equiped Grob 109, with the Limbach 2000cc VW engine, up above 10,000' I use climb setting to take off,
then cruise setting from about 3000 AGL to 9000 AGL
then climb setting from 9000 to 12,000 AGL
then cruise setting above 12,000 AGL

I can not tell you the scientific reason for this, and perhaps it has something to do with the auto leaning function
of the Stromberg carbs but I just know that this technique works for me.

I tested it specifically on a hot day ~100F at ground level 1250 MSL so that I could see if I would be able to get over the Sierra's in California on a no lift day.

Honestly the climb rate was in the low hundreds FPM after ~10k but it does continue to climb regardless, just takes some time.

[Edit by jb92563 on Monday, April 5, 2010 @ 03:48 PM]

Posted Thursday, April 15, 2010 @ 10:44 AM  

The Hoffman V62 pitch change mechanism is a centrifugal type unit hence the rpm for up and down shifting (1500 rpm or less to shift to climb pitch and 2200 rpm or more to shift to cruise pitch)

That being the case the pre engine start routine is to pull the pitch change lever to cause the prop to go into climb (take off) pitch since the rpm is less than 1500.

Also the pre landing checklist also has an item to make sure the prop is in climb pitch in case a go around is required and maximum thrust (climb) is required.

I do however always land with the engine shut down so that should I nose over by overly vigourous brake application I will not damage the engine and prop. I ussusally shut down mid downwind since it free wheels for a while an needs a bit of time to come to a stop.

I dont feather in the pattern because I might need to restart in a hurry should a go around be required.

We have skydivers at my airport and sometimes they land on the runway and actually pick up their laundry and walk down the center of the runway home. (They must be delerious from the adenaline, like flirting with death or have a screw loose but I have seen happen more than a few times)