X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from nm8-vm0.bullet.mail.bf1.yahoo.com ([98.139.213.95] verified) by logan.com (CommuniGate Pro SMTP 5.4.6) with SMTP id 5644452 for flyrotary@lancaironline.net; Mon, 09 Jul 2012 15:45:21 -0400 Received-SPF: none receiver=logan.com; client-ip=98.139.213.95; envelope-from=ceengland@bellsouth.net Received: from [98.139.215.142] by nm8.bullet.mail.bf1.yahoo.com with NNFMP; 09 Jul 2012 19:44:45 -0000 Received: from [68.142.200.221] by tm13.bullet.mail.bf1.yahoo.com with NNFMP; 09 Jul 2012 19:44:44 -0000 Received: from [66.94.237.100] by t9.bullet.mud.yahoo.com with NNFMP; 09 Jul 2012 19:44:44 -0000 Received: from [127.0.0.1] by omp1005.access.mail.mud.yahoo.com with NNFMP; 09 Jul 2012 19:44:44 -0000 X-Yahoo-Newman-Id: 847181.82076.bm@omp1005.access.mail.mud.yahoo.com Received: (qmail 79657 invoked from network); 9 Jul 2012 19:44:44 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bellsouth.net; s=s1024; t=1341863084; bh=1CoUS0OmYbaABe3WPTU2YZK7zegxgUAc+fe7vbN5Ong=; h=X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Message-ID:Date:From:User-Agent:MIME-Version:To:Subject:References:In-Reply-To:Content-Type; b=5bdUnB9BVd9ymxFPJSksFPMhJzdSeiYrgvMGDmSY2Vo+DbcO+TdDKEopEDXf05vFFf2GZLHzOeOT9D5/s04fPxDnF8yzJO1fsAHuqmQGUyKwoJ0fsSJXezy6coPXQDlm8IDVfGhRJSjWH8K7/lpiTE88n8ao93COM5I0Arzdz7k= X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: PTK1lF8VM1m22Nr5YfPcaHZoQiUAalHXOr13W681r5D2qQj aee2mRFbksJDmsKVjYHjWDORkLUYFW_XmBNALOBVVtp5kl6y2T9pew9bVpnr Rjp8N7k_GzqPT4oT6PF0lcYfN5LL1Rmpt828WRji0oOImYGcHQ5MIv4HAjt_ AkEVW_4qiV5YmfvPu4kTNOfJE61lyJLkJFPIsKUZr7_OBRMXrCCUIsZIyjTx EUbv4Rtr3urV6T4ZTZtM5oyHYrMplN3ZiCFfbGKL8nT.KNV4pAah4GZwxdMo n9O0O13nFYLQypEy.kMEJ3Q8C8.DP1I8Gt87gyDyM10s7nJ2yiYneVj5MiUq 5RLh9UJcIwRbI_LQmaTyHUcJLmB.w4ip74_XcrZC7smBTj4XjTqt_.hcbBqF XSAKv3AiYcBLVbL_l10hP6xYIsPwEN_26BhxjrwopXU6xfNR7HAqg68SWD3y R X-Yahoo-SMTP: uXJ_6LOswBCr8InijhYErvjWlJuRkoKPGNeiuu7PA.5wcGoy Received: from [192.168.10.30] (ceengland@98.95.167.162 with plain) by smtp108.sbc.mail.mud.yahoo.com with SMTP; 09 Jul 2012 12:44:43 -0700 PDT Message-ID: <4FFB34AB.4060701@bellsouth.net> Date: Mon, 09 Jul 2012 14:44:43 -0500 From: Charlie England User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0.1) Gecko/20110929 Thunderbird/7.0.1 MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: On the step References: In-Reply-To: Content-Type: multipart/alternative; boundary="------------090406090102020307030404" This is a multi-part message in MIME format. --------------090406090102020307030404 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Hi Bill, There's something seriously outside the norm if he's only getting 150 kts at 8k ft full throttle. Any properly built -7 will come very close to Van's spec performance numbers. The fixed pitch prop would have little effect on cruise, if pitched properly for the plane & HP. 160 hp -7's with FP props can easily hit that cruise figure. Charlie On 07/09/2012 02:02 PM, Bill Bradburry wrote: > > Brian, > > Getting "on the step" might get you at your terminal velocity/hp/rpm > equilibrium sooner, but no matter when, at some time it will all level > out at the equilibrium point. You might be able to dive and pick up > 9% more, but it will not hold and will eventually bleed off the same > point no matter how you got there. > > It seems true that you can judge the rotary hp by its rpm, but in the > case of the shallow dive, you are actually reducing the load on the > prop and the engine uses the hp not needed to pull the plane to > increase the prop rpm. When the load from the plane comes back, when > you level out, the rpm will drop back because the hp is now being used > to pull the plane as before. If this didn't work this way, you could > carry a plane with a 3 hp lawnmower engine up to 30K feet and drop it > out and the engine would be producing 10,000 hp by the time it got > down to sea level!! It would then level out and maintain mach 2!!! :>) > > My next door hangar neighbor has an RV-7 with a 200HP fixed pitch prop > and he is pretty consistently running 150 knots of true airspeed at 8K > feet. You could probably use him as a guide for performance on your > plane. At 8K feet he is at close to 75% power. Say 150 HP. > > B2 > > ------------------------------------------------------------------------ > > *From:*Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] > *On Behalf Of *bktrub@aol.com > *Sent:* Monday, July 09, 2012 12:43 PM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] On the step > > I commented on here recently about how I took a cross- country flight > to Walla Walla from Everett, Wa recently and was only seeing 140-150 > mph cruise at 11,500 feet. It got me to thinking- I was getting about > 6200 rpm on the engine which is 2175 at the prop. So, I'm a little > overpropped/ underpowered. > > So, there's the old chestnut about how you can get a few more knots > from an airplane in cruise if you go a little above your cruise > altitude and then descend to your cruise altitude, thereby getting "on > the step" . Some pilots swear by this, others dismiss it. I have a > theory- if I climb to a cruise altitude and stay at full throttle > while doing so, I will only get the engine to run up to a certain RPM > and therefore a certain hp will be achieved, and no more and so the > airplane will settle into an equilibrium at a certain speed- say at > whatever hp/speed - 140 mph at 6200 rpm- lt's say x hp. > > Now, If I were to descend to my cruise altitude in a shallow dive, I > will be acheiving a higher rpm and hence horsepower, say 6800 rpm and > horsepower will be x + 9%x for a hp of 109% of the hp achieved at 6200 > rpm, so I should be able to achieve and maintain a higher cruise > speed if I descend to my cruising altitude. ( I picked 9% arbitrarily > for the sake of argument) . > > Anyone want to shoot me down on this one? > > This is just an theory, If I want to go faster first I have to clean > up my drag. My cooling scoop is effective, but obviously draggy. And > It needs a flap on it. That's a project for this winter. > > Brian Trubee > --------------090406090102020307030404 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Hi Bill,

There's something seriously outside the norm if he's only getting 150 kts at 8k ft full throttle. Any properly built -7 will come very close to Van's spec performance numbers. The fixed pitch prop would have little effect on cruise, if pitched properly for the plane & HP. 160 hp -7's with FP props can easily hit that cruise figure.

Charlie


On 07/09/2012 02:02 PM, Bill Bradburry wrote:

Brian,

 

Getting “on the step” might get you at your terminal velocity/hp/rpm equilibrium sooner, but no matter when, at some time it will all level out at the equilibrium point.  You might be able to dive and pick up 9% more, but it will not hold and will eventually bleed off the same point no matter how you got there.

 

It seems true that you can judge the rotary hp by its rpm, but in the case of the shallow dive, you are actually reducing the load on the prop and the engine uses the hp not needed to pull the plane to increase the prop rpm.  When the load from the plane comes back, when you level out, the rpm will drop back because the hp is now being used to pull the plane as before.  If this didn’t work this way, you could carry a plane with a 3 hp lawnmower engine up to 30K feet and drop it out and the engine would be producing 10,000 hp by the time it got down to sea level!!  It would then level out and maintain mach 2!!!  :>)

 

My next door hangar neighbor has an RV-7 with a 200HP fixed pitch prop and he is pretty consistently running 150 knots of true airspeed at 8K feet.  You could probably use him as a guide for performance on your plane.  At 8K feet he is at close to 75% power.  Say 150 HP.

 

B2

 

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of bktrub@aol.com
Sent: Monday, July 09, 2012 12:43 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] On the step

 

I commented on here recently about how I took a cross- country flight to Walla Walla from Everett, Wa recently and was only seeing 140-150 mph cruise at 11,500 feet. It got me to thinking- I was getting about 6200 rpm on the engine which is 2175 at the prop. So, I'm a little overpropped/ underpowered.

 

So, there's the old chestnut about how you can get a few more knots from an airplane in cruise if you go a little above your cruise altitude and then descend to your cruise altitude, thereby getting "on the step" . Some pilots swear by this, others dismiss it. I have a theory- if I climb to a cruise altitude and stay at full throttle while doing so, I will only get the engine to run up to a certain RPM and therefore a certain hp will be achieved, and no more and so the airplane will settle into an equilibrium at a certain speed- say at whatever hp/speed - 140 mph at 6200 rpm- lt's say x hp.

 

Now, If I were to descend to my cruise altitude in a shallow dive, I will be acheiving a higher rpm and hence horsepower, say 6800 rpm and horsepower will be x + 9%x for a hp of 109% of the hp achieved at 6200 rpm, so I should be able to achieve and maintain a higher cruise  speed if I descend to my cruising altitude. ( I picked 9% arbitrarily for the sake of argument) .

 

Anyone want to shoot me down on this one?

 

This is just an theory, If I want to go faster first I have to clean up my drag. My cooling scoop is effective, but obviously draggy. And It needs a flap on it. That's a project for this winter.

 

Brian Trubee


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