Return-Path: Received: from [24.25.9.102] (HELO ms-smtp-03-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.3c2) with ESMTP id 761012 for flyrotary@lancaironline.net; Sat, 26 Feb 2005 20:44:05 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.102; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-185-127.carolina.rr.com [24.74.185.127]) by ms-smtp-03-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j1R1hBkd003152 for ; Sat, 26 Feb 2005 20:43:12 -0500 (EST) Message-ID: <003e01c51c6d$b77e5510$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" Subject: Monster Prop Air Brake Date: Sat, 26 Feb 2005 20:43:20 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_003B_01C51C43.CE6577B0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_003B_01C51C43.CE6577B0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Went to the RV Flyin in Richmond, KY today. Lots of RVs from Ohio = Valley Region and the East Coast. Only one rotary, but a lot of = interest. This new prop/gear box is really great. I climbed to 11,500 = ft from 1000 ft runway in 11 minutes so average closed to 1000 fpm. At = 11,500 the rate of climb was 600 fpm - better than the old Cessna 150 at = sea level {:>). For those of you interested, I found out by experimenting (at a higher = altitude than last time {:>)), another possible answer why I lost 20 mph = airspeed within approx 100-125 ft of travel on landing Feb 12 that = resulted in a HARD landing including dragging the rudder.=20 In my original message on the topic I speculated that it could have been 1. Had not allowed sufficient margin for the gusty wind conditions 2. Trees and hangers that were on the upwind side of my touch down = point may have perturbed or blocked the flow so that when I got within = their shadow (leeward side),where I lost considerable airspeed very = quickly=20 3. I should have paid more attention to other pilots who have reported = "down drafts" in that area (including one who reminded me today, that = he had touched down 20 ft short of the runway on that same approach with = his wife on board (for her first flight with him) and he claimed he = still had above stall airspeed when he hit the grass. But, hey I had = been flying out that airport for 4 years and never had encountered one = (well, until Feb 12 that is {:>)) 4. Every once in a while everything stacks up NOT-IN-YOUR-FAVOR! Monster Prop Air Brake Well, I will add one more possibility (perhaps the most likely). I = found out today by experimentation that with the big monster prop = (76,88) that if I pull the power back sufficiently, the airspeed decays = very rapidly. Let me explain - It appears that so long as I have the = prop turning over fast enough so that it is providing a "no drag" to the = air flow - everything is just fine. However if I lower the power such = that the prop is no longer a "no drag" component air speed decays much = faster than with my old prop. For instance if I am doing 89-90 mph (as if on final) with the engine = turning around 2800-3200 rpm everything is just fine. However, if (as I = recall doing on that hard landing) I retard the throttle to around 2000 = rpm (which I did that day as I was slightly over shooting my touch down = point) , the air speed decreases rapidly and the rate of descent goes up = considerably. Never had that type of thing happen with the smaller prop = or at least not to any noticeable extent. I speculate that the combination of the larger disk area (25%) of the = 76 vs the 68 inch prop dia and the 2.85:1 gear box offering more = resistance to the airstream turning the prop (compared to the 2.17). So = if the prop is turning at least fast enough so that is not a drag, = there is no noticeable effect, but once the engine is retarded to where = it becomes a drag component to the air stream - it apparently be comes a = "BIG" drag component. So don't know whether this theory holds water, but the effect is there = and I found today that keep the engine at 3200 rpm resulted in a = considerably difference. Any ideas from you prop guys?? Ed=20 Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com ------=_NextPart_000_003B_01C51C43.CE6577B0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Went to the RV Flyin in Richmond, KY = today. =20 Lots of RVs from Ohio Valley Region and the East Coast.  Only one = rotary,=20 but a lot of interest.  This new prop/gear box is really = great.  I=20 climbed to 11,500 ft from 1000 ft runway in 11 minutes so average closed = to 1000=20 fpm.  At 11,500 the rate of climb was 600 fpm - better than the old = Cessna=20 150 at sea level {:>).
 
For those of you interested, I found = out by=20 experimenting (at a higher altitude than last time {:>)), another = possible=20 answer why I lost 20 mph airspeed within approx 100-125 ft of = travel on=20 landing Feb 12 that resulted in a HARD landing including dragging the = rudder.=20
 
In my original message on the topic I = speculated=20 that it could have been
 
1.  Had not allowed sufficient margin for the gusty wind=20 conditions
 
2.  Trees and hangers that were on the upwind side of = my touch=20 down point may have perturbed or blocked the flow so that when = I got=20 within  their shadow (leeward side),where I lost=20 considerable airspeed very quickly 
 
3.  I should have paid more attention to other pilots who have = reported "down drafts" in that area (including one who reminded me = today,=20  that he had touched down 20 ft short of the runway on that same = approach=20 with his wife on board (for her first flight with him) and he claimed he = still=20 had above stall airspeed when he hit the grass.  But, hey I had = been flying=20 out that airport for 4 years and never had encountered one (well, until = Feb 12=20 that is {:>))
 
4.  Every once in a while = everything stacks up=20 NOT-IN-YOUR-FAVOR!
 
Monster Prop Air Brake
 
Well, I will add one more possibility (perhaps the most = likely).  I=20 found out today by experimentation that with the big monster prop = (76,88)=20  that if I pull the power back sufficiently, the airspeed decays = very=20 rapidly. Let me explain -  It appears that so long as I have = the prop=20 turning over fast enough so that it is providing a "no drag" to the air = flow -=20 everything is just fine.  However if I lower the power such that = the prop=20 is no longer a "no drag" component air speed decays much faster than = with my old=20 prop.
 
For instance if I am doing 89-90 mph (as if on final) with the = engine=20 turning around 2800-3200 rpm everything is just fine.  However, if = (as I=20 recall doing on that hard landing) I retard the throttle to around 2000 = rpm=20 (which I did that day as I was slightly over shooting my touch down = point) , the=20 air speed decreases rapidly and the rate of descent goes up = considerably. =20 Never had that type of thing happen with the smaller prop or at least = not to any=20 noticeable extent.
 
I speculate that the combination of the  larger disk area = (25%)=20 of the 76 vs the 68 inch prop dia and the 2.85:1 gear box offering more=20 resistance to the airstream turning the prop (compared to the = 2.17).  So if=20 the prop is  turning at least fast enough so that is not a drag,=20  there is no noticeable effect, but once the engine is retarded to = where it=20 becomes a drag component to the air stream - it apparently be comes a = "BIG" drag=20 component.
 
So don't know whether this theory holds water, but the effect is = there and=20 I found today that keep the engine at 3200 rpm resulted in a = considerably=20 difference.  Any  ideas from you prop guys??
 
Ed
 
 
 
Ed Anderson
Rv-6A N494BW Rotary=20 Powered
Matthews, NC
eanderson@carolina.rr.com
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