Today's Message Index:
----------------------
1. 08:00 AM - Re: MT Propeller Update (flyv35b)
2. 02:21 PM - Re: MT Propeller Update (Bruce Smith)
3. 03:53 PM - Re: TeamGrumman-List Digest: 2 Msgs - 12/29/03 (Tiger67B)
Message 1
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| Subject: | Re: MT Propeller Update |
--> TeamGrumman-List message posted by: "flyv35b" <flyv35b@juno.com>
> It climbs well, but the benefits of constant speed are lost in the 2500
rpm
> red line imposed by the STC.
And herein lies the key IMO, along with the cost and probability that the
plane will be measureably slower than it is with the Sensenich prop, why the
prop will not be very popular or sell well.
For years Dick Van Grunsven and Van's Aircraft has been very interested in
evaluating performance of the RV aircraft with various props. And
considerable testing was done in conjunction with the CAFE 400 races back in
1990 with numerous wood props.
More recently Van's Aircraft has evaluated performace with both fixed pitch
and constant speed props and recently published the results in the "RV
Aviator". The tests were conducted with a 180 hp RV-8 operating at "optimum
cruise speed". That was defined as the speed attainable at 8000' altitude
and 75% power (full throttle) and 2500 rpm. 2500 rpm because that, even
though 2700 rpm is the rated rpm for the engine, most pilots would not be
comfortable operating at 2700 rpm continuously for cruise operation. This
criteria was chosen as the most important performance criteria for most
pilots. Climb rates with the various CS prop varied by about 2-5%.
All of the props tested (6 constant speed and one fixed pitch) were 2 blade
except for a 3 blade Whirlwind and a 3 blade MT wood/composite, the
configuration recommended by MT. The poorest performing prop was the 3
blade MT, which was 8.2 mph slower than the best prop, a new 2 blade
Hartzell "blended airfoil", which resulted in 208.9 mph. The 3 blade
Whirlwind prop (at 203 mph) was 3.7 mph slower than the 2 blade whirlwind
prop. The 2 blade fixed pitch Sensenich prop resulted in a speed of 207.9
mph at 2500 rpm and 210.9 mph at 2700 rpm. This Sensenich prop was
essentially designed for the RV aircraft and is quite similar to the 76"
dia. one used on the Tiger.
According to the article "conventional knowledge holds that, everything else
being equal, adding prop blades with result in reduced performance". This
has also been true with the 2 and 3 bladed props used on the IO-520 powered
Bonanzas until recently when Hartzell introduced their new 3 blade "blended
airfoil" prop for it. I recently bought one of these props for my Bonanza
and it does perform quite well. The Scimitar blade tip design has allowed
an increase of 2 in. diameter over the 3 blade McCauley and still reduce the
noise level, resulting in better takeoff and climb performance. Hartzell
told me that this prop was also slightly faster than the original 2 blade
McCauley. And this is contrary to the conventional knowledge mentioned
above thanks to Hartzell's ability to machine a blade with a continuous
change in airfoil for optimum efficiency and noise reduction. I paid $7800,
including the beautiful spinner assembly, for this 82 in. dia. prop and am
very happy with it.
*All of the comments made here pertaining to the test results, etc. were
taken from an article written by Van in the most recent RV Aviator
newsletter.
Cliff A&P/IA
----- Original Message -----
From: <TeamGrumman@aol.com>
Subject: TeamGrumman-List: MT Propeller Update
> --> TeamGrumman-List message posted by: TeamGrumman@aol.com
>
> I talked to an FAA guy with experience certifying an MT prop on a
Cherokee.
> He told me they did the certification for 2700 rpm redline.
>
> He also suggested I look up the Type Certificate Data Sheet for the prop
and
> see if it spells out what the design red line is.
>
> So I did.
>
> But First...
>
> I flew the MT prop a couple more times. As I might have mentioned, the
> controller is set to operate at 1500-2500 rpm. After flying the plane,
at
> anything much above 15 to 18 inches manifold pressure, the pop won't pull
down to
> 1500 rpm with the controller set to 1500 rpm.
>
> From the little experience I have flying the plane with the MT prop, it
looks
> like the engine operating range should be in the 1800 to 2700 rpm range.
> Perhaps, to be perfectly honest, with a lot of flying time, I could see
> justification for anything below 2000 rpm. As it is, even with the
controller set to
> 2500 rpm, flying a touch and go pattern is a piece-O-cake. I'm not clear
as
> to why anyone would need to set the engine to 1500 rpm.
>
> As for the TCDS redline. the prop looks like it's designed for 210-220 hp
and
> 2800 rpm.
>
> It climbs well, but the benefits of constant speed are lost in the 2500
rpm
> red line imposed by the STC.
>
> Gary
>
>
Message 2
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| Subject: | Re: MT Propeller Update |
tests=FROM_HAS_MIXED_NUMS, FROM_HAS_MIXED_NUMS3
--> TeamGrumman-List message posted by: Bruce Smith <res02p3h@verizon.net>
Cliff and all,
New technology (or at least mid 80's tech since the blended airfoils and
flaps on the trailing edges of the blades were really pioneered during
the research conducted for the "propfans" developed by both GE and
Hamilton Standard) are cool. However, they usually involve increased
complexity. Therein lies the rub. The beauty of the Grummans is their
performance AND simplicity. A fixed pitch prop isn't sexy, but it
usually is reliable, and not prone to cause pilot error, ie. go around
with the prop in high pitch. It gets the job done. So, while it's nice
that someone is going the route of STC'ing the MT prop, where is the
value for the $10K+? I agree with Gary, it looks cool. But, I've gotten
1000 fpm climb in the Tiger I rent, so where is the return on investment?
If I had a couple of million dollars, I'd get with Gary and Bruce Catto
and see if I could concoct a better (composite) fixed pitch prop. Till
the lottery comes my way, I'm gonna rely on a good old Sensenich fixed
pitch prop.
Happy New Year to all!!!!
Bruce Smith
flyv35b wrote:
>--> TeamGrumman-List message posted by: "flyv35b" <flyv35b@juno.com>
>
>
>
>>It climbs well, but the benefits of constant speed are lost in the 2500
>>
>>
>rpm
>
>
>>red line imposed by the STC.
>>
>>
>
>And herein lies the key IMO, along with the cost and probability that the
>plane will be measureably slower than it is with the Sensenich prop, why the
>prop will not be very popular or sell well.
>
>
>
Message 3
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| Subject: | Re: TeamGrumman-List Digest: 2 Msgs - 12/29/03 |
--> TeamGrumman-List message posted by: Tiger67B <jnpsavage@cox.net>
JUST IN CASE YOU DIDN'T SEE THIS......
AOPA ePilot Special Airspace Bulletin December 30, 2003
A special notice to AOPA members in and near southern Nevada
==> ATTENTION PILOTS <==
FAA EXPECTED TO ESTABLISH TFR OVER LAS VEGAS
AOPA is sending this message to advise you that airspace restrictions
are expected over New Year's Eve celebrations in Las Vegas tomorrow,
December 31.
According to the FAA, the notam is expected to create a temporary
flight restriction (TFR) within a 20-nm radius of McCarran
International Airport, with an extension to the southeast around the
Hoover Dam, from the surface to 18,000 feet msl. All pilots will be
required to squawk a discrete transponder code and maintain two-way
communication with ATC. There will also be a 6-nm-radius no-fly zone
centered on the airport that prohibits all general aviation flight
activities from the surface to 18,000 feet msl. The restrictions will
be effective from 8 p.m. local time tomorrow, December 31 (New Year's
Eve), until 3 a.m. local on Thursday, January 1 (New Year's Day).
As of 3 p.m. Pacific time Tuesday, a notam establishing the TFR
had not been issued.
The full text of any notams implementing this anticipated airspace
restriction will be posted on AOPA Online as soon as possible after
they are issued ( http://www.aopa.org/whatsnew/notams.html ).
"Security-related TFRs usually single out general aviation aircraft,
which have never been used in a terrorist attack," said AOPA President
Phil Boyer. "The restrictions are an additional burden for pilots to
carry. AOPA believes they should only be issued based on credible
threats--not for a political need to be seen taking strong measures."
Because TFR airspace frequently changes, AOPA strongly encourages
pilots to obtain a briefing and CHECK NOTAMS before every flight.
TFR violators will be intercepted and forced to land.
==> HELPFUL WEB LINKS <==
AOPA's Real-Time Flight Planner provides up-to-the-minute graphical
depictions of TFRs ( http://www.aopa.org/flight_planner/ ).
Check the FAA's TFR Web site ( http://tfr.faa.gov ).
Download the AOPA Air Safety Foundation's intercept procedures card
( http://download.aopa.org/epilot/2003/intercept.pdf )or review ASF's
"Know Before You Go" program ( http://www.aopa.org/asf/know_before/ ).
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