X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 12 Jun 2006 01:14:06 -0400 Message-ID: X-Original-Return-Path: Received: from wind.imbris.com ([216.18.130.7] verified) by logan.com (CommuniGate Pro SMTP 5.0.9) with ESMTPS id 1149818 for lml@lancaironline.net; Sun, 11 Jun 2006 12:12:35 -0400 Received-SPF: none receiver=logan.com; client-ip=216.18.130.7; envelope-from=brent@regandesigns.com Received: from [192.168.1.100] (vsat-148-63-101-227.c002.t7.mrt.starband.net [148.63.101.227]) (authenticated bits=0) by wind.imbris.com (8.12.11/8.12.11.S) with ESMTP id k5BGBfK5015755; Sun, 11 Jun 2006 09:11:44 -0700 (PDT) (envelope-from brent@regandesigns.com) X-Original-Message-ID: <448C40B4.4040207@regandesigns.com> X-Original-Date: Sun, 11 Jun 2006 09:11:32 -0700 From: Brent Regan User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 X-Original-To: Bruce Ryan , Lancair Subject: IVP Props with Beta References: In-Reply-To: Content-Type: multipart/alternative; boundary="------------050900060704000107080902" This is a multi-part message in MIME format. --------------050900060704000107080902 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Bruce, I installed an MT 4 blade reversing (beta) prop on my IV-P because I operate out of a 2200' field at 2,700 AGL, frequently with a tailwind. I wanted the reversing function for supplemental / emergency use. The MT prop uses a proprietary (custom) governor that has a solenoid to actuate the high pressure Beta circuit. There is a mechanical interlock in the prop hub that prevents the beta from being actuated above 1500 RPM. For prop control I used a standard control cable. I put a momentary contact (beta) switch at the base of the throttle control that I can push with my index finger while simultaneously advancing the throttle. This works very well and eliminated the complexity of an intricate mechanism. The biggest downside of a reversing prop is FOD. During landing, after slowing enough so that the prop is >1,500 RPM, when Beta is actuated it blows dust and small rocks up in front of the airplane, which the plane then rolls through. Ouch. I have rock chips on the front surface of the blades. These are better, however, than an off runway excursion and not nearly embarrassing as a bird strike on the tail. I had originally anticipated that beta would also be used on a semi regular basis, reducing brake wear and maintenance costs. In practice I rarely use it, usually only during practicing emergency procedures. Beta would be useful in the event of a brake failure, poor traction or a botched short field landing. I would absolutely recommend a counterweighted feathering prop configured such that a loss of engine oil pressure does NOT result in an engine over-speed. I know of one illustrative case that started with a cracked turbo oil supply fitting. The pilot noted fluctuating oil pressure and wisely elected to reduce power and perform a precautionary landing. When the nose was lowered the oil pickup was un-ported and the oil pressure dropped below the minimum required by the governor. The engine over-speeded, requiring a prop and engine tear down. A problem that could have been fixed with a $10 fitting and a case of oil turned into a $20,000 repair and 8 weeks of AOG. I would only recommend Beta if you frequent short or slippery runways or are prone to land long and fast. It is a nice safety net to have if you ever need it. Regards Brent Regan Bruce Ryan wrote: > Brent > I have gotten to the point where I have to zero in on a prop > configuration for my IVP (TSIO550) > > I definitely will go feathering for better glide ratio, but have been > thinking about a reversible (BETA) prop after listening to a few IVPT > folks comment on the usefulness. I probably will not do a lot of short > field work, but here in the NE runways are often covered with snow and > additional drag/breaking would offer a good safety margin. > > I think someone mentioned that you had a reversing prop and if so I > wonder if I could ask a few question > > * What mfg (MT?) > * Reliability/mfg support? > * What prop governor is required? > * Did you also install an accumulator? > * What type of prop control/lockout did you use? > * Would you do it again? > * Which feathering only ( non reversal) prop seems to be the best > match for the IVP/TSIO550 > * Any important thing I forgot to ask?! > > Many thanks > Regards > Bruce > --------------050900060704000107080902 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Bruce,

I installed an MT 4 blade reversing (beta) prop on my IV-P because I operate out of a 2200' field at 2,700 AGL, frequently with a tailwind. I wanted the reversing function for supplemental / emergency use. The MT prop uses a proprietary (custom) governor that has a solenoid to actuate the high pressure Beta circuit. There is a mechanical interlock in the prop hub that  prevents the beta from being actuated above 1500 RPM. 

For prop control I used a standard control cable. I put a momentary contact (beta) switch at the base of the throttle control that I can push with my index finger while simultaneously advancing the throttle. This works very well and eliminated the complexity of an intricate mechanism.

The biggest downside of a reversing prop is FOD. During landing, after slowing enough so that the prop is >1,500 RPM, when Beta is actuated it blows dust and small rocks up in front of the airplane, which the plane then rolls through. Ouch. I have rock chips on the front surface of the blades.  These are better, however,  than an off runway excursion and not nearly embarrassing as a bird strike on the tail.

I had originally anticipated that  beta would also be used on a semi regular basis, reducing brake wear and maintenance costs. In practice I rarely use it, usually only during practicing emergency procedures. Beta would be useful in the event of a brake failure, poor traction or a botched short field landing.

I would absolutely recommend a counterweighted  feathering prop configured such that a loss of engine oil pressure does NOT result in an engine over-speed. I know of one illustrative case that started with a cracked turbo oil supply fitting. The pilot noted fluctuating oil pressure and wisely elected to reduce power and perform a precautionary landing. When the nose was lowered the oil pickup was un-ported and the oil pressure dropped below the minimum required by the governor. The engine over-speeded, requiring a prop and engine tear down. A problem that  could have been fixed with a $10 fitting and a case of oil turned into a $20,000 repair and 8 weeks of AOG.

I would only recommend Beta if you frequent short or slippery runways or are prone to land long and fast. It is a nice safety net to have if you ever need it.

Regards
Brent Regan


Bruce Ryan wrote:
Brent
I have gotten to the point where I have to zero in on a prop configuration for my IVP (TSIO550)
 
I definitely will go feathering for better glide ratio, but have been thinking about a reversible (BETA) prop after listening to a few IVPT folks comment on the usefulness. I probably will not do a lot of short field work, but here in the NE runways are often covered with snow and additional drag/breaking would offer a good safety margin.
 
I think someone mentioned that you had a reversing prop and if so I wonder if I could ask a few question
  • What mfg (MT?)
  • Reliability/mfg support?
  • What prop governor is required?
  • Did you also install an  accumulator?
  • What type of prop control/lockout did you use?
  • Would you do it again?
  • Which feathering only ( non reversal) prop seems to be the best match for the IVP/TSIO550
  • Any important thing I forgot to ask?!
Many thanks
Regards
Bruce
 
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