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teamgrumman(at)YAHOO.COM
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 Posted: Mon Oct 04, 2010 7:39 pm Post subject: Jaguar cowling with the stock muffler STC |
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The first question the FAA will ask (through the DER) is, "Is the cowling exactly the same as it was with the exhaust system previously tested and approved?"
The answer is, "No."
The next question is, "Is the pressure drop across the cylinders exactly the same as it was with the cowling/muffler combination previously tested and approved?"
The answer is, "I don't know."
The next question is, "Does the possible change in pressure in the area under the cowling near where the carb heat gets its air affect the carb heat rise temperature?"
The answer is, "I don't know."
The next question is, "Does the possible change in pressure and air flow paths in the area under the cowling affect the temperature of the accessories (mags, vacuum pump, etc.)?"
The answer is, "I don't know."
The next question is, "Does the exhaust pipe hanging out further forward and coming through the affect climb performance?"
The answer is, "I don't know."
The next question is, "Do you have approved drawings for the proposed changes?"
The answer is, "No."
So, without approved data, tests will need to be performed to determine just what the answers are.
It seems like it would be easy to certify the cowling with the stock muffler, doesn't it. I mean, hey, the stock Tiger has one. What many of you fail to grasp is just what changing a small thing like the muffler would entail. There is absolutely nothing 'logical' about getting an STC. It's all about examining every possible affect a change makes and then investigating that possibility and how it MIGHT affect the safety of the airplane.
Case in point: The carb heat rise with the Power Flow Exhaust System (PFES) was approved for the stock cowling. The Jaguar cowling, in no way, has any affect on the ability of the PFES to generate enough heat to pass the carb heat rise test. I created a company test report, with pictures, explaining how the cowling does not affect carb heat rise tests. Yet, someone in the FAA felt like it may be possible that the change in pressure drop across the cylinders could 'possibly' cause the pressure at the inlet into the PFES carb heat portion of the muffler/collector to reduce the ability to achieve the required 90 degree temperature rise at the carb inlet. Those tests, alone, took 3 months and thousands of dollars.
Case in point: It's fairly obvious that the Jaguar cowling creates less drag. I had to complete 5 climb performance tests at gross weight to show I met or exceeded the performance of the POH. Those 5 flight tests took 2 months to complete.
If you've seen any of the initial pictures of my plane with the Jaguar cowling on it, you'll see it had the stock muffler. Less than a year after those pics were taken, the entire side of the stock muffler blew out and cooked the inside of the cowling. I'm a hot rodder at heart and I know the benefits of the PFES. I ordered a Power Flow the next day. It wasn't a question I needed to ponder for very long.
From: flyv35b <flyv35b(at)minetfiber.com>
To: teamgrumman-list(at)matronics.com
Sent: Mon, October 4, 2010 2:43:15 PM
Subject: Re: Re: Power Flow Exhaust System
--> TeamGrumman-List message posted by: "flyv35b" <flyv35b(at)minetfiber.com (flyv35b(at)minetfiber.com)>
| Quote: | What Jim wants is what the majority of owners need, what Gary is offering is what the minority of owners want.
Gary's desire is to design improvements in both design and performance and the new cowl with PF scores on both these fronts, but is it what most need. ?
There is no doubt in my mind if the cowl had gone with the stock exhaust sales would have been easier to come by. Would Gray have been happy with the results, no as thankfully for the future development of our planes he always strives for the best at the expense of self reward.
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It is my OPINION that getting the STC amended to include the stock exhaust would not be nearly as onerous as Gary mentioned (2-3 years and $15,000).
| Quote: | From a logical point of view why would it be so hard to get approval when
that is the stock system and Gary has shown that the cooling is better with his cowl than with the stock configuration. And the PF would not materially affect cooling, except to possibly make it worse due to the higher power output of the engine. The FAA should just rubber stamp the approval, but logic does not prevail a lot of times with them. Having the cowling approved for BOTH exhaust systems would more than double the market size I would think.
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Cliff
----- Original Message ----- From: "grumpyparts" <i.r.m(at)btinternet.com (i.r.m(at)btinternet.com)>
To: <teamgrumman-list(at)matronics.com (teamgrumman-list(at)matronics.com)>
Sent: Monday, October 04, 2010 2:25 PM
Subject: Re: Power Flow Exhaust System
| Quote: | --> TeamGrumman-List message posted by: "grumpyparts" <i.r.m(at)btinternet.com (i.r.m(at)btinternet.com)>
What Jim wants is what the majority of owners need, what Gary is offering is what the minority of owners want.
Gary's desire is to design improvements in both design and performance and the new cowl with PF scores on both these fronts, but is it what most need. ?
There is no doubt in my mind if the cowl had gone with the stock exhaust sales would have been easier to come by. Would Gray have been happy with the results, no as thankfully for the future development of our planes he always strives for the best at the expense of self reward.
Oh BTW, notice my message just contains my reply and doesn't contain every thing that has gone before. Try not to just add your response to an existing thread and hit the send key.
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deej(at)deej.net
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| Posted: Tue Oct 05, 2010 6:03 am Post subject: Jaguar cowling with the stock muffler STC |
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On 10/04/2010 11:32 PM, Gary Vogt wrote:
| Quote: | It seems like it would be easy to certify the cowling with the stock
muffler, doesn't it. I mean, hey, the stock Tiger has one. What many
of you fail to grasp is just what changing a small thing like the
muffler would entail. There is absolutely nothing 'logical' about
getting an STC. It's all about examining every possible affect a change
makes and then investigating that possibility and how it MIGHT affect
the safety of the airplane.
|
Which is precisely why a lot of us are turning to experimental
aviation. We've over-regulated ourselves right out of the certified
market, making the price so high that us mere mortals can't afford to
play there anymore. If you just want to fly and not play, certifieds
are great for that.
With my budget I can't even contemplate paying multiple thousands of
dollors for an exhaust system or a cowling. Just no way I could afford
to do it. But I can fabricate my own exhaust or cowling for an
experimental for the cost of materials and my labor, and when I am
working for myself, my labor is cheap! 
I really applaud you guys pursuing the STC options for our aircraft. I
wish there were a way we could make the process a lot easier and cheaper
so more of us could afford to enjoy the fruits of your efforts.
-Dj
--
Dj Merrill - N1JOV
Glastar Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/
Please use Netiquette Guidelines http://tools.ietf.org/html/rfc1855
Kindly TRIM your email replies and post AFTER the relevant text
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grumpyparts
Joined: 28 Jan 2009
Posts: 65
Location: EGHH
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| Posted: Tue Oct 05, 2010 9:12 am Post subject: Re: Jaguar cowling with the stock muffler STC |
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| Quote: | | What many of you fail to grasp is just what changing a small thing like the muffler would entail. |
So it would be interesting to know whether Power Flow had all the same hoops to jump through when getting the STC for the Standard cowling and again when they changed it from external to internal.
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