[f-AA] metal prop for Lasher STC

[Joe Preston]

Just curious if anyone has gone through the process of finding which Sensenich or other metal prop is approved for the Lasher STC C-85-12 upgrade?

I have a M74CK46 that is 72.5" long that I would like to install at some point. I also have an approved wooden one as well, but want to have a backup metal one.

 

I spoke with David Lasher and his Grandfather is not doing well. This is very unfortunate but not unexpected. David said he is unable to ask him anymore technical questions. The STC instructions do not mention any specific metal props. Anyone have any thoughts?

 

JoeP

 

[Jim Spee]

Hi Joe,

Just follow the Type Certificate Data Sheet for the 7DC:

http://www.hangar9aeroworks.com/AeroncaTechInfo/A-759.pdf

Propeller Limits Static rpm at maximum permissible throttle setting: (For
fixed pitch Not over 2465, not under 2300. No additional tolerance
permitted. wood propeller) Diameter: not over 72 in., not under 70 in.

1. Wood Propellers - fixed pitch 10 lb.
Models 7AC, 7BCM, 7CCM, 7DC (-52)
Models 7EC,7FC, 7JC (-54)
(a) Sensenich 72C-44 (Models 7AC and S7AC)
Sensenich 72CK (Model 7BCM)
Sensenich 72CK-44, -45, -46 (Models 7DC, S7DC)
Sensenich 72GK-48, -49, -50 (Models 7CCM, 7EC, S7CCM, 7FC, 7JC)
(b) Flottorp 72A50, 52 (Models 7CCM, S7CCM, 7EC, 7FC, 7JC)
(c) Any other approved fixed pitch wood propeller which is eligible for the
engine power and speed and which meets the diameter and static r.p.m. limits
specified under "Propeller Limits" for the pertinent model.

2. McCauley 1A90 with following limits: 26 lb.(-52)

(a) (7AC and S7AC) Static r.p.m. at maximum permissible throttle setting:
Not over 2250 (for 7AC), 2200 (for S7AC), not under 2100 (for 7AC or S7AC).
No additional tolerance permitted. Diameter: not over 71 in., not under 69.5
in.

(b) (7BCM only) Static r.p.m. at maximum permissible throttle setting: Not
over 2450, not under 2350. No additional tolerance permitted. Diameter: not
over 71 in., not under 69.5 in.

(c) (7DC only) Static r.p.m. at maximum permissible throttle setting: Not
over 2465, not under 2300. No additional tolerance permitted. Diameter: not
over 71 in., not under 69.5 in.

Sensenich M76AK-2 metal propeller with following limitations: 23 lb.
Models 7AC, 7BCM, 7CCM, 7DC (-52)
Models 7EC,7FC, 7JC (-54)

(a) (Models 7CCM, S7CCM) Static r.p.m. at maximum permissible throttle
setting: Not over 2410, not under 2150. No additional tolerance permitted.
Diameter: not over 74 in., not under 72.5 in.

(b) (Models 7EC, 7FC, 7JC) Static r.p.m. at maximum permissible throttle
setting: Not over 2350, not under 2150. No additional tolerance permitted.
Diameter: not over 74 in., not under 72.5 in.

(c) (Model S7EC) Static r.p.m. at maximum permissible throttle setting: Not
over 2400, not under 2300. No additional tolerance permitted. Diameter: not
over 74 in., not under 72.5 in.

(d) (Models 7AC, 7BCM, 7DC) Static r.p.m. and diameter limits same as for
fixed pitch wood propeller under applicable.

Looks like you need to trim down to 72" diameter.

Jim in Redlands who is trading a 74" 1A90 for a 69.5" 1A90.

7BCM Champ N81724
jim_...@hotmail.com
james...@redlands.edu
Redlands, California, USA

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[Joe Preston]

Thanks Jim,
I thought about that as well, but the aircraft is a 7AC CONV not a 7DC. In
addition, the text below doesn't cover metal Sensenich CK props. It does for
wood ones, but the metal ones mentioned are AK props.
Having said that, I looked a little further and the TCD does list the
Sensenich M74CK for a 7AC, but that is for an A-65 engine. I have a C85-12.
Am I restricted to only what is listed on the STC?
JP

[Jim Spee]

Hi Joe,

The STC (which I also own) converts your aircraft to a 7DC for purposes of
the Type Certificate. Here is the key line:

(d) (Models 7AC, 7BCM, 7DC) Static r.p.m. and diameter limits same as for
fixed pitch wood propeller under applicable.

The question is would that mean that another model prop is still acceptable?

Jim

[Tom Holmes]

Isn't there a line in there that says "or other propellers that meet these specifications"?

Tom

Jim Spee <jim_...@hotmail.com> wrote:

[Jim Spee]

Hi Tom,

Couldn't find that line in the TCDS. I found this tho:

0.
Senenich fixed pitch metal 21 lb. (-52)
(a) M74CK (Models 7AC, S7AC)

Static r.p.m. at maximum permissible throttle setting:

Not over 2250, not under 1960.
Diameter: not over 74 in., not under 72 in.
(b) M74CK-2 (Model 7BCM)

Static r.p.m. at maximum permissible throttle setting:

Not over 2450, not under 2200.

Diameter: not over 72 in., not under 70 in.

I'm not sure why they don't mention 7DC since they have the same engine.

Jim from Rancho Cucamonga campus of University of Redlands

7BCM Champ N81724
jim_...@hotmail.com
james...@redlands.edu
Redlands, California, USA

[Robert Poules]

Joe,
When i upgraded my engine to a C 85, i used the Wagner STC
The STC called for a metal Sensenich 74 CK x --- (blank)..
I further upgraded my C-85-12 with the 0200 crank STC.
I bought and installed a new Sensenich 74 CK X 46 , (as you have) and
it climbs out great with a cruise of 100 mph..
My static prop. rpm. range is within the spec. of the stc.
Bob Poules

[Joe Preston]

Thanks Bob,
That is very helpful and I am sure from a practical standpoint as long as I
keep wthin the static RPM, I will be fine. Having said that, from a legal
nit-picking standpoint, (which one has to take in regards to the federales -
sorry Gregg) I am not under the Wagner STC. So where does that leave me?
Jim Spee,
To save e-mail space, I wiill reply here. I have a C-85-12. If I am not
mistaken the 7DC has a C-85-8 does it not? The quote you had in the TCD said

a) M74CK (Models 7AC, S7AC)
Static r.p.m. at maximum permissible throttle setting:
Not over 2250, not under 1960.

Well, I will most certainly be over that RPM with this engine. The range is
between 2300 and 2575 RPM. Again, I am not trying to pick nits here and I
know that the prop I have will work as long as I can get the static RPM, but
is it legal?

thanks for all the replys so far.
JP

-----Original Message-----
From: aeronca...@westmont.edu
[mailto:aeronca...@westmont.edu]On Behalf Of Robert Poules
Sent: Friday, May 09, 2008 12:39 AM
To: aer...@westmont.edu; J...@Preston-Company.com
Subject: Re: [f-AA] metal prop for Lasher STC

[Gregg Horrell]

Joe,
Give me a call at work on Monday and we'll discuss some options.

907-790-7307

Gregg Horrell

[Jim Spee]

Hi Joe,

Here's where the "Supplemental" in STC comes in. Lasher has supplemented
the Type Certificate to allow the C-85-12 insted of the C-85-8, so you
should still be able to file your 337 using approved data and not ask for
approval. Does that sound right, Gregg?

Jim in Redlands off to pick up some Aeronca parts

7BCM Champ N81724
jim_...@hotmail.com
james...@redlands.edu
Redlands, California, USA

>From: "Joe Preston" <J...@Preston-Company.com>

>Reply-To: aer...@westmont.edu, J...@Preston-Company.com
>To: <aer...@westmont.edu>

[Gregg Horrell]

Hi Jim,
Without having read the Lasher STC I can't answer that accurately. The
short answer is "No".
- Aircraft Specification A-759 Revision 70 dated January 9, 2008 covers
the 7 Series Aeronca
- A-759 Section I describes the 7AC with a Continental A-65-8 and says
"See Note 4 for optional engines and conversion to other models"
- Note 4 allows conversion to 7BCM or 7DC with a C-85-8 with the
appropriate propellers for those models

You do not have approved data to install the 7BCM or 7DC propeller on
the Lasher STC unless it is stated on the STC.

Someone please scan and email me a copy of the Lasher STC so I can review
it. ryan...@gci.net

Gregg Horrell

[Jim Spee]

Hi Gregg,

Good idea! My copy of the STC is at Redlands Airport. I'll scan a copy and
shoot it off to you by Monday. Here is some data from Service Letter 14:

( c ) Any of the following propellers may be used on Model 7DC airplanes.

Sensenich Model 72GK44
Sensinich Model 72GK45
McCauley CF7144
McCauley CF7146

If the above listed or other make or pitch wood propellers are used, the
propeller installed must meet the diameter and static RPM limits listed for
the Model 7DC under "Propeller Limits" in the Specification A759. (See also
Item 1 ( c ) Aircraft Specification A-759).

No mention of metal props in the Service Letter.

Jim
--------------------------------------------------
From: "Gregg Horrell" <ryan...@gci.net>
Sent: Friday, May 09, 2008 5:40 PM
To: <aer...@westmont.edu>

[Tom Holmes]

Jim Spee <jim_...@hotmail.com> wrote:

Hi Gregg,

Good idea! My copy of the STC is at Redlands Airport. I'll scan a copy and
shoot it off to you by Monday. Here is some data from Service Letter 14:

( c ) Any of the following propellers may be used on Model 7DC airplanes.

Sensenich Model 72GK44
Sensinich Model 72GK45
McCauley CF7144
McCauley CF7146

If the above listed or other make or pitch wood propellers are used, the
propeller installed must meet the diameter and static RPM limits listed for
the Model 7DC under "Propeller Limits" in the Specification A759. (See also
Item 1 ( c ) Aircraft Specification A-759).


No mention of metal props in the Service Letter.

Jim
--------------------------------------------------
From: "Gregg Horrell"

Sent: Friday, May 09, 2008 5:40 PM
To: