X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fmailhost02.isp.att.net ([207.115.11.52] verified) by logan.com (CommuniGate Pro SMTP 5.2.14) with ESMTP id 3684103 for flyrotary@lancaironline.net; Tue, 16 Jun 2009 09:52:41 -0400 Received-SPF: pass receiver=logan.com; client-ip=207.115.11.52; envelope-from=bbradburry@bellsouth.net Received: from desktop (adsl-230-68-117.mco.bellsouth.net[74.230.68.117]) by isp.att.net (frfwmhc02) with SMTP id <20090616135202H0200p3tp7e>; Tue, 16 Jun 2009 13:52:02 +0000 X-Originating-IP: [74.230.68.117] From: "Bill Bradburry" To: "'Rotary motors in aircraft'" References: In-Reply-To: Subject: RE: [FlyRotary] Re: Not developing full power. Date: Tue, 16 Jun 2009 09:52:12 -0400 Message-ID: <56BD694A9D7E4501893E217E7D377085@Desktop> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0000_01C9EE68.1F7EE870" X-Mailer: Microsoft Office Outlook 11 Thread-Index: Acnt2sPGqE60P8ZRSiCsb4pKG7S1KQAq/wqg X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6001.18049 This is a multi-part message in MIME format. ------=_NextPart_000_0000_01C9EE68.1F7EE870 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Steve, What results has your repaired muffler given you? =20 It strikes me that you should be able to get over 6K static (and take = off) RPM with the 2.17 drive. That shouldn=92t change much with altitude I = think. You will have less air for the engine to breathe, but it will be easier = for the prop to turn in the thinner air. You were getting about 5K on your = take off and climb from Texas. Your climb rate was only about 400 fpm also. = You lifted off at close to 1K feet at 6 minutes and reached close to 4K feet = at 14 minutes. Lets say 3200 ft in 8 minutes. At higher altitudes I = don=92t know if you could climb.?? Do you think all this was caused by the = muffler? Your prop rpm was right in there with your indicated airspeed. Both = were about 148-149 mph at cruise. =20 If you still have throttle left after the engine maxes out, I think = that indicates a problem of some kind. I encourage you to try and discover = what causes it. One reason is that I am having the same situation! :>) My static is around 5400 rpm max and there is still throttle left. I am = still working on my cooling, so I can not run the engine. But I don=92t think = I am developing enough power to try to fly. Where did you get the data? =20 Bill B =20 =20 _____ =20 From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of sboese Sent: Monday, June 15, 2009 12:59 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Not developing full power. The following observations may be of interest in the light of recent discussions. =20 =20 On the flight to the resent Rotorfest, I thought the exhaust noise level = had increased at one point. This was just chalked up to fatigue and the = longer than normal time in flight since this was the longest XC attempted to = date. My usual procedure for adjusting throttle position is to advance it = until no further increase in rpm results even though there is normally about =BC = of the total travel still available. My throttle body is a cut down Mazda one = with two openings as described in Tracy=92s guide. Since I use the stock oil metering pump, the throttle position adjusts the metering pump stroke = and advancing the throttle more than necessary results in accumulation of = oil in the sump. At one point when checking the throttle position, the RPM actually dropped slightly when advancing the throttle further. I = thought to myself =93this is strange=94 and returned the throttle to its original = setting since things were running smoothly. =20 At the Rotorfest, I listened with interest to Mark=92s presentation on = muffler lifetime or lack thereof, wondering why my first attempt at a muffler = had survived so long. I attributed this to my normal operation at high = density altitudes which results in reduced max power levels. I also described = the construction of my =93bomb=94 to several people who were interested in = it. I now realize that I didn=92t know what was in it myself. During the = preflight before leaving the Rotorfest, I noticed a rattle in the muffler when checking its security to the belly of the plane. After returning to Laramie, I investigated the rattle further and the results are shown in = the attached pictures. The fact that the center baffle broke is not = surprising since it was simply a push fit into the shell and was vulnerable to = flexing since it was flat. The repair uses a conical shaped baffle with a solid ring around its outside circumference to make it even stiffer. We=92ll = see how long that lasts. =20 The recent discussion on not developing full power, especially Ed=92s information on seeing almost 20 gph at max power settings at seal level = got me thinking about my performance. I have seen up to 16 gal/hr at 4500 = ft DA on a rare excursion to that low an altitude. That didn=92t seem = unreasonable considering the sophistication of my setup compared to Ed=92s. Looking = back at the data log from the flight home from the Rotorfest, there were some interesting observations concerning the departure from 40XS. That = segment of some of the data from the log is shown in the attached plots. =20 A couple of things in the data seem to me to stand out. One is that I = am recovering nearly full manifold pressure in the plenum at wide open = throttle compared to ambient as shown in the data of the manifold pressure before start-up and during runup and take off. This has always been the case. = The second thing that stands out is that I was only using between 10 and 11 gal/hr at wide open throttle with the mixture adjusted for max power. I didn=92t look at the fuel flow reading during runup or take off and only noticed these low values when examining the data log recently. I am confident that the fuel flow readings are quite accurate since the fuel actually used for this trip matches the instrument readout very well. = While some of you may have experienced some apprehension at such a pathetic = power production level, it seemed normal to me since I usually operate at = density altitude from 7000-10000 ft. Another thing I noticed in the data is the significant rpm drop when the prop unstalled just prior to liftoff. The = rpm usually drops a little at that point but not nearly this much. I = remember noticing this on departure, but was otherwise occupied and didn=92t give = much further thought at the time. Not shown in the plots is the coolant temperature which reached 225 degrees at the stock location in the = flywheel end iron at 8 minutes into the log. This is about 20 degrees higher = than normal even at the reduced fuel consumption level during this time. Oil temperature showed a similar response. =20 After removing the muffler to investigate the rattle, standing it on end would allow the broken segment to move to the area of the outlet and = block some of the exhaust exit area. Laying it horizontally again would allow = the broken segment to slide down the conical end where it could not be seen = in the exit. I suspect that the exhaust gas carried the broken segment up = the slope where it could block part of the exit when operating at power = levels above idle. Luckily, the blockage was not enough to prevent generating enough power to sustain flight. =20 In any case, the data log is a record of the effect of increased back pressure on the performance of my NA 13B. Just as has been described in = the recent discussions, the result was as expected: decreased max fuel consumption and decreased max power production. In addition, I saw increased coolant and oil temperatures. Maybe the increased back = pressure was responsible for the decrease in rpm upon fully opening the throttle = in stabilized flight, but I=92m not sure why such an effect would arise. =20 For what it is worth=85 =20 Steve Boese =20 ------=_NextPart_000_0000_01C9EE68.1F7EE870 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Steve,

What results has your repaired muffler given you?=A0 =

It strikes me that you should be able to get over 6K static (and = take off) RPM with the 2.17 drive.=A0 That shouldn’t change much with = altitude I think.=A0 You will have less air for the engine to breathe, but it will = be easier for the prop to turn in the thinner air.=A0 You were getting about 5K on = your take off and climb from Texas.=A0 Your climb rate was only about 400 fpm also.=A0 You lifted off at close = to 1K feet at 6 minutes and reached close to 4K feet at 14 minutes.=A0 Lets = say 3200 ft in 8 minutes.=A0 At higher altitudes I don’t know if you could = climb.??=A0 Do you think all this was caused by the = muffler?

Your prop rpm was right in there with your indicated = airspeed.=A0 Both were about 148-149 mph at cruise. =A0

If you still have throttle left after the engine maxes=A0 out, I = think that indicates a problem of some kind.=A0 I encourage you to try and = discover what causes it.=A0 One reason is that I am having the same situation!=A0 = :>)=A0 My static is around 5400 rpm max and there is still throttle left.=A0 I am = still working on my cooling, so I can not run the engine.=A0 But I don’t = think I am developing enough power to try to fly.

Where did you get the data?

 

Bill B

 

 

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of sboese
Sent: Monday, June 15, = 2009 12:59 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = Not developing full power.

=

The following observations may be = of interest in the light of recent discussions. 

 

On the flight to the resent = Rotorfest, I thought the exhaust noise level had increased at one point.  This = was just chalked up to fatigue and the longer than normal time in flight since = this was the longest XC attempted to date.  My usual procedure for adjusting throttle position is to advance it until no further increase in rpm = results even though there is normally about =BC of the total travel still available.  My throttle body is a cut down Mazda one with two = openings as described in Tracy’s guide. Since I use the stock oil metering pump, the throttle position = adjusts the metering pump stroke and advancing the throttle more than necessary = results in accumulation of oil in the sump.  At one point when checking the throttle position, the RPM actually dropped slightly when advancing the throttle further.  I thought to myself “this is = strange”  and returned the throttle to its original setting since things were = running smoothly.

 

At the Rotorfest, I listened with = interest to Mark’s presentation on muffler lifetime or lack thereof, = wondering why my first attempt at a muffler had survived so long.  I attributed = this to my normal operation at high density altitudes which results in reduced = max power levels.  I also described the construction of my = “bomb” to several people who were interested in it.  I now realize that I didn’t know what was in it myself.  During the preflight = before leaving the Rotorfest, I noticed a rattle in the muffler when checking = its security to the belly of the plane.  After returning to Laramie, I investigated the rattle = further and the results are shown in the attached pictures.  The fact that = the center baffle broke is not surprising since it was simply a push fit = into the shell and was vulnerable to flexing since it was flat.  The repair = uses a conical shaped baffle with a solid ring around its outside circumference = to make it even stiffer.  We’ll see how long that = lasts.

 

The recent discussion on not = developing full power, especially Ed’s information on seeing almost 20 gph at = max power settings at seal level got me thinking about my performance.  = I have seen up to 16 gal/hr at 4500 ft DA on a rare excursion to that low an altitude.  That didn’t seem unreasonable considering the sophistication of my setup compared to Ed’s.  Looking back at = the data log from the flight home from the Rotorfest, there were some = interesting observations concerning the departure from 40XS.  That segment of = some of the data from the log is shown in the attached = plots.

 

A couple of things in the data seem = to me to stand out.  One is that I am recovering nearly full manifold = pressure in the plenum at wide open throttle compared to ambient as shown in the = data of the manifold pressure before start-up and during runup and take = off.  This has always been the case.  The second thing that stands out is that = I was only using between 10 and 11 gal/hr at wide open throttle with the = mixture adjusted for max power.  I didn’t look at the fuel flow = reading during runup or take off and only noticed these low values when examining the = data log recently.  I am confident that the fuel flow readings are quite = accurate since the fuel actually used for this trip matches the instrument = readout very well.  While some of you may have experienced some apprehension at = such a pathetic power production level, it seemed normal to me since I usually = operate at density altitude from 7000-10000 ft.  Another thing I noticed in = the data is the significant rpm drop when the prop unstalled just prior to liftoff.  The rpm usually drops a little at that point but not = nearly this much.  I remember noticing this on departure, but was otherwise = occupied and didn’t give much further thought at the time.  Not shown = in the plots is the coolant temperature which reached 225 degrees at the stock location in the flywheel end iron at 8 minutes into the log.  This = is about 20 degrees higher than normal even at the reduced fuel consumption = level during this time.  Oil temperature showed a similar = response.

 

After removing the muffler to = investigate the rattle, standing it on end would allow the broken segment to move to = the area of the outlet and block some of the exhaust exit area.  Laying = it horizontally again would allow the broken segment to slide down the = conical end where it could not be seen in the exit.  I suspect that the exhaust = gas carried the broken segment up the slope where it could block part of the = exit when operating at power levels above idle.  Luckily, the blockage = was not enough to prevent generating enough power to sustain = flight.

 

In any case, the data log is a = record of the effect of increased back pressure on the performance of my NA = 13B.  Just as has been described in the recent discussions, the result was as expected: decreased max fuel consumption and decreased max power production.  In addition, I saw increased coolant and oil temperatures.  Maybe the increased back pressure was responsible = for the decrease in rpm upon fully opening the throttle in stabilized flight, = but I’m not sure why such an effect would = arise.

 

For what it is = worth…

 

Steve = Boese

 

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