Tie down for high power run on a 14A

[1949MGTC]

Getting ready for first flight. I’ve tried twice now on my 14A to chock the wheels on concrete for a high power run to set max rpm on the prop/engine. Twice I’ve started sliding and have now crushed an aluminum chock. Any suggestions on how to tie it down or should I just do a run down the runway to check the max rpm?

Thanks
Bill Gardner
140849
N513DB

 

[Carl Froehlich]

I suggest you stop here.

If you must do a static run, then tie the tail to a pickup truck or such.

There is reason why high speed taxi tests are out of favor. I suggest you make sure the engine responds as normal, do a mag check at ~1800 RPM or so, then do first fight. Kill the engine if RPM does not come up shortly after initial roll.

Carl

 

[andoman]

Amen, Carl.
Full power runups are asking for a prop ding from sucking a stone through the prop (or worse if something lets go), and a high speed full power "taxi" is asking for is a no man's land were bad things can happen fast.

 

[Kyle Boatright]

Bed in your brake pads per the manufacturer's guidance first, then use brakes and chocks (big wooden chocks, no wheel pants) to do your runup.

Clear the area of debris so you don't suck up a pebble.

You do need to do a full rpm runup before your first flight and properly set your low pitch stop. I know of a -10 that hit 3,000 rpm on its first flight because the builder didn't know about setting the low pitch stop.

 

[Bavafa]

As Carl said, tie to to a truck or car preferably by the gearleg.

But I do recommend a short static run to set/adhyst the prop speed and also check the fuel flow at max power. In fact my static run has been to pull the tail down to simulate a climbing attitude to make sure the engine will run at full power for a few minutes.

 

[PaulvS]

Van discouraged high speed taxi testing because it can easily lead to an inadvertent and unplanned first flight.
I'm not sure that the tail tie down point is designed to take a horizontal force e.g. from restraining a full power run up.
At least in my part of the world, a full power run is conducted prior to first flight to confirm that power and fuel flow will be sustained during the initial climb out.

 

[BobTurner]

You do need to do a full rpm runup before your first flight and properly set your low pitch stop. I know of a -10 that hit 3,000 rpm on its first flight because the builder didn't know about setting the low pitch stop.

Actually two low pitch stops: one mechanical one on the prop, the other on the governor.

I agree with Kyle: read the brake pad manufacturer’s instructions to condition the pads.

 

[Draker]

I did this test several times on my -7A. Tied each gear leg to my truck with ratchet straps high up where the leg enters the fuselage, and then wrapped a third ratchet strap below the ties, to keep the straps from sliding down the legs.

I'm glad I did the test. I found my governor was set wrong and I was not making even close to full power. Glad I found and corrected it before first flight.

 

[BillL]

Be Prepared -

Definitely anchor to a truck. I ran the front tires over a pull strap, and used a backpack blower to pre clear the area of debris.

A 14 friend did not anchor, and the tach was off. Then pulled the prop at speed and it hopped over a couple of 4X4 blocks. It was headed for a hangar, - - did I mention the brakes were not bedded and would not stop it? Fortunately, he recovered and hit nothing and no one. A LESSON for others.

A prop can produce up to 800 lbs thrust. Be prepared.

 

[DanH]

Tied each gear leg to my truck with ratchet straps high up where the leg enters the fuselage,

Right on. Whenever possible. yoke to the top of the main gear legs. Remove the chocks. Clear area ahead, just in case.

The typical 1" wide ratchet straps sold at discount stores don't inspire much confidence. Minimum would be quality 1/2" polyester rope rigged two-part. Fours will be 500 to 1000 lbs static thrust, and a hotrodded -10 will be more.

Tying to a tailwheel spring is generally ok, but it is possible to pull the tail tiedown point out of an A-model. We had a local mechanic who proved it.

 

[AX-O]

some additional advice.

loop the strap as low as possible on your truck to keep the tail from coming up. I do this by looping the strap through the lowest spoke/tire combo. If you use the hitch or some other higher point, by the time the tail accidentally comes up, it is too late.


The other best option is using an airport ground tie down ring and placing the tailwheel right on top (or centered between the main landing gear). then use the strap to tie everything down.

 

[Tommy123]

If you have to do a power assurance check make sure there is plenty of empty space in front of you in case it gets away from you.

 

[Webb]

Light pole works if one is handy.

 

[VA Maule]

Full power test

Here’s how I rigged mine to set the initial ground adjustable prop pitch. One long 4” nylon strap from the gear legs threaded through the tail wheel fork ( nose wheel could tie up the big straps to the rear tie down ring ) . A second strap attached to the other straps to keep them from slipping down from the top gear legs . Secured the my pickup truck