[f-AA] Static RPMs

[Harvey Brock]

  I just put a rebuilt A75 on my Champ. It seems my static RPMs are a little low but I can't recall what my other engine static RPMs were at full throttle. Of course, this was the first start up and warm up. I haven't replaced the cowl nor all baffles pending inspection by my AI.

   For those of you flying with an A75, what static RPMs are you seeing at full throttle?

Harvey, who is searching old records for history on the previous engine.

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[Roger Anderson]

Do you have the appropriate A75 prop on it?

Sent from my iPad

[Harvey Brock]

It is the same prop I've always had. Both engines are A75. 

  It's just that I almost never did a static, full throttle test because of weak brakes. I'll have to check to answer which Sensenich metal prop I have.

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From: aer...@westmont.edu <aer...@westmont.edu> on behalf of Roger Anderson <11...@comcast.net>
Sent: Saturday, November 23, 2019 6:19:11 PM
To: aer...@westmont.edu <aer...@westmont.edu>
Subject: Re: [f-AA] Static RPMs

 

[Roger Anderson]

Oh. Ok. Thought you might have been going up from an A65. 

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[Richard Murray]

If I recall correctly the A75 had a different carb listed on its TCDS but since you went A75 to A75 are you sure the throttle is opening fully?

Richard in OH exhausted after spending the day at an auction where they had a lot of airplane stuff

[Harvey Brock]

  I found the prop info: Sensenich MK74CK-2. I didn't find any previous report of full throttle static RPMs.

Harvey, who discovered there was landing gear damage in 1948 while searching records.

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From: aer...@westmont.edu <aer...@westmont.edu> on behalf of Roger Anderson <11...@comcast.net>

Sent: Saturday, November 23, 2019 6:36:44 PM

[Harvey Brock]

Yep Richard,

    Throttle moves stop-to-stop with the same carb as before. I re-used my carb since it always started easy. I don't really know RPMs are low but it seems a little low at full throttle, wheels chocked. I suspect it would make more RPMs if I were rolling or climbing.

     This might just be imagination. I just figured it would be good to check with this group before I button everything back together. ( Especially since I can't recall a full throttle static RPM check)

Harvey, who remembers less than I should.

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From: aer...@westmont.edu <aer...@westmont.edu> on behalf of Harvey Brock <harve...@hotmail.com>
Sent: Saturday, November 23, 2019 7:26:13 PM

[Duane Fey]

Harvey,

I still have the log book from your first A75.  I’ll take a look at it when I get home.

Duane

‘46 Chief, N85981

[Richard Holcombe]

It all depends on the prop.

[Harvey Brock]

  Thanks Duane,

      I'm figuring since both of mine are A75 and running the same prop, then I should see the same static RPMs if both engines are developing the same horsepower. My error of never actually checking static full throttle RPMs on the previous engine leaves me without a good comparison for the new engine. So, I'm not sure if I'm imagining lower RPMs or if I need to check/adjust/repair or replace something before assembling the cowl and nosebowl.

  Any reports are appreciated. I should have checked RPMs before removing the engine.

Harvey, who remembers Bugs Bunny saying, "I should have taken that left turn in Albuquerque"

Sent from my Samsung Galaxy Tab®4

-------- Original message --------
From: Duane Fey <duan...@gmail.com>
Date:11/23/2019 9:29 PM (GMT-06:00)
To: aer...@westmont.edu
Subject: Re: [f-AA] Static RPMs

[Roger Anderson]

You got me curious.  I thumbed through Google.  I read one place for an A75 Continental says 2150 - 2250 static.  Another discussion said 2200ish to 2300ish.  And then it was mentioned it's going to depend on whether the prop is climb, standard, or cruise.  I have no idea what my Chief does.  The brakes don't hold that well.  Guess out of curiosity now, I'll maybe chock it and see what it does for static.  Doesn't really matter if it is running and performing good for me though.  My opinion.  

[Harvey Brock]

Thanks  Roger, 

  That is where mine is performing. And, I used chocks because brakes alone aren't sufficient to hold it.

Harvey, hoping nothing is wrong with my new engine. 

[Tom Boyle]

Harvey, with no hard info on the engine before it was reworked you'll only be able to go on what info you have from it now.  An A75 should get about 2250 static with the right prop.  The right prop is actually shorter than the one used for the A65 by two inches putting it at 70 inches.  This allows the engine to put out higher RPM's to develop the additional 10 Hp.  It gets the Hp into the air stream with a courser pitch.  Whatever,  it sounds as though your engine is healthy.

Tom

On 11/24/2019 8:33 AM, Harvey Brock wrote:

Thanks  Roger, 

  That is where mine is performing. And, I used chocks because brakes alone aren't sufficient to hold it.

Harvey, hoping nothing is wrong with my new engine. 

[Harvey Brock]

Thanks,

   This is really what I was asking. Just something to compare to.

Sent from my Samsung Galaxy Tab®4

-------- Original message --------
From: Tom Boyle <tomb...@charter.net>
Date:11/24/2019 9:05 AM (GMT-06:00)
To: aer...@westmont.edu

[Gib Valbert]

That's what A/C specs. are for.

[Richard Murray]

Gib you are absolutely correct.

What someone should have suggested is to look up the Champ TCDS A-759

and we find that the 7 series has been certificated for a whole lot of engines, but not the A-75.

This means Harvey has to have an STC from someone who did the engineering to prove the A-75 was an acceptable substitute to put on his Champ. That STC paperwork should have specified the length of propeller to be used and the static rpm range.

In the absence of any guidance in the 7AC TCDS we must turn to the A-75 TCDS E-213 which only lists the maximum continuous rpm at 2600.

Neither Sensenich for wood or metal nor McCauley for metal list the A-75 engine specifically.

If we search STCs we find SA3-435 which permits the A-75 installation on Chiefs and Champs. You have the follow Owens Service Letter 2 dated 10-08-60 for 7AC Champs for guidance.

I don't have nor could I find any reference to Owens Service Letter 2. I do have a copy of Owens Service Letter 1, which came with a Chief I own that has an A-75, and I have attached it for reference.

From Owens Service Letter 1 we find the props he suggests suitable for the A-75 and the static and red line rpm defined.

Richard in OH who is grateful Gil reminded us there is a pathway to finding information about certificated aircraft and would appreciate learning what STC was used to put an A-75 on Harvey's Champ

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Each sunrise is an opportunity to learn more than you knew the day before.

[Mark Peterson]

Which reminds me of the old timer wisdom is to use all the A-75 parts in the overhaul, but don't change anything else.  List the parts as the ones that are replaced, but don't call it a A-75.   You can put the new prop on and no one is officially the wiser.   As far as the paperwork is concerned, it's a overhauled A-65 with the holes in the connecting rods improvement.

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From: aer...@westmont.edu <aer...@westmont.edu> on behalf of Richard Murray <murra...@gmail.com>
Sent: Sunday, November 24, 2019 5:28 PM
To: aer...@westmont.edu <aer...@westmont.edu>

[Roger Anderson]

And......that's the way I see life....and so did my Dad...I think.   Oh..and the old A65 I parted out, yep, did have the holes in the connecting rods.    And the A65 manual I have that was my Dad's, yep, has a pencil drawing by him of the corect drilling of the holes in connecting rods.  roger

[cham...@gmail.com]

Owens holds the STC for the Champ A75.  I bought one for $50 about a dozen years ago. 

Regards, Bruce 

[Harvey Brock]

   I had to pay $250.00 for the STC on my previous Chief. The interesting point is the same engine was on the Chief for several years before I bought it. Then, at first annual, the AI failed a cylinder for low compression. Holes were in the rod caps and the prop was specified for A75. He wouldn't complete theinspection without the STC.

   I have an STC for this Champ as well as several 337s. I'll look there when time permits. Once again, work interferes with my flying.

I never thought to check the STC.

Harvey, who can't find the screwdriver I just had in my hand.