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I haven't looked it up, but would wonder if these limits are valid for "standard" conditions of if the range given is to help take into account for this?
 
- Jason


From: Ed Burkhead [mailto:[EMAIL PROTECTED]
Sent: Tuesday, June 20, 2006 11:35 AM
To: 'heavensounds'; Ctech
Subject: RE: [COUPERS-TECH] Short on power

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Eliacim,

 

Couple of considerations:

 

  1. Static rpm is what you get on the ground with full power in a zero wind condition.  (On a windy day, I’ve approximated no-wind condition by turning the propeller plane sideways to the wind.  It’s not exactly the same as no-wind conditions but it’s much closer than having your nose into the wind.  Don’t overheat the engine.)

 

2.  By Aircraft Specification A-718:

SPECIFICATIONS PERTINENT TO ALL MODELS

. . .

2. Propeller - fixed pitch metal, McCauley 1A90CF or 1B90CM 26 lb. (-32)

(a) With Continental C-75 series engines only

static r.p.m. at maximum permissible throttle

setting: not over 2100, not under 1950.

No additional tolerance permitted.

Diameter: not over 73 in., not under 71 in.

 

  1. I’d go by the electronic tach.  By that, your 1920 rpm is below the minimum.

 

  1. Don’t expect red line rpm on the ground.  It won’t happen.  When you get forward motion, the rpms may go up to the redline of (correct me if I’m wrong) 2275 rpm for a C-75.

 

  1. Do you know what the pitch is of your prop?  Is it a climb, normal or cruise prop?  That’ll affect where you should be within the allowed range of 1950-2100 static rpm.

 

It does sound like you have some lack of power but go by your experts, not me.  I know little about mechanical issues.

 

Ed Burkhead

http://edburkhead.com

ed -at- edburkhead???.com          (change -at- to @ and remove "???")

 

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