X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from an-out-0708.google.com ([209.85.132.240] verified) by logan.com (CommuniGate Pro SMTP 5.1.10) with ESMTP id 2190252 for flyrotary@lancaironline.net; Fri, 20 Jul 2007 19:48:21 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.132.240; envelope-from=rotary.thjakits@gmail.com Received: by an-out-0708.google.com with SMTP id b2so193478ana for ; Fri, 20 Jul 2007 16:47:45 -0700 (PDT) DKIM-Signature: a=rsa-sha1; c=relaxed/relaxed; d=gmail.com; s=beta; h=domainkey-signature:received:received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; b=OsyoM7z3hUhuBBskRH5wthcWdHf23xBpbW9kThhZkjqtc64w+Od+ldpsl+qMfmuCBdA0N2ZKEI5xIJx3NarCPkGtu1W23As7G8qnS2kKd2PSbsCEzMlb0OiPGw93YaRt72unokUG2g13+FYxwqVVEu4EzJb06uK+h0Glm23BbxY= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; b=cGD7gsHJCRg5FhAeG1EGhvvUiv1l2SXhUQmd1TatovqjXAnP4cbW6s5TXsBRWyqh+lP1GgUGHbPdm3Rm20TGqAMbHZ9ymEVTbh1eVceYGRB6BtrTqDtwFpKqhPECKWectc9AVURwdHsML9wLXKiG6inysFEgAyGUpTT69EgfvI0= Received: by 10.100.107.2 with SMTP id f2mr518483anc.1184975264983; Fri, 20 Jul 2007 16:47:44 -0700 (PDT) Received: by 10.100.197.17 with HTTP; Fri, 20 Jul 2007 16:47:44 -0700 (PDT) Message-ID: <63163d560707201647h64dcde3fycf81dc067ee18bd2@mail.gmail.com> Date: Fri, 20 Jul 2007 18:47:44 -0500 From: "Thomas Jakits" To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] FW: [FlyRotary] Re: Thrust measure. In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_176025_23287141.1184975264945" References: ------=_Part_176025_23287141.1184975264945 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline Hi Pat, whether a prop produces "worthwhile" thrust at 0 forward speed depends on your application. Remember the Davis DA-9 (??) or so, with Ken Schuggert (?) as the pilot? His prop was stalled up to about 50 kts(?), idling down the runway (because it would make more thrust idling than at rpm), until it started to bite.. Long take-off roll, but would go like stink once at speed. For a CH-801, speed is of no concern, acceleration is everything - static thrust IS getting interesting here! I assume as a dyno it would be interesting to have a special static prop to load the engine and eventually it can be used to compare engines/mods/etc. with this one prop as a baseline. Whether this dyno prop has any aviation use at all doesn't matter, it puts some serious load on the engine. How to calibrate this prop is a different question, but just to see, whether an engine runs better or worse than before it is good enough.... """"snip" > Ok... I've seen countless little red biplanes hang from their prop at > airshows; certainly the prop is "stalled", and knowing that the engine/prop > combination can produce thrust to counter the gross weight in order to allow > the plane to hover is useful information to this small group of pilots. But > how many of us really need that info? > > > """snip" If that prop is stalled the bird comes down!! Just because the plane has zero speed, does not mean the prop is stalled. In this case it rather works like a inefficient, but effective rotor, vertical inflow speed should be rather impressive. If you observe: Non of these stunts starts with a standing motor - they always pull up and slowly reduce speed and adjust rpm/pitch. At this point a inflow inertia gets established ( I guess it takes about 1-3 seconds, wild guess from helo experience) and kept there with excess power. I don't know how close they are to a real stall - but at this moment they are NOT stalled. You would hear the engine overspeed and the plane accelerate tailwards!! :)) TJ ------=_Part_176025_23287141.1184975264945 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline
Hi Pat,
 
whether a prop produces "worthwhile" thrust at 0 forward speed depends on your application.
Remember the Davis DA-9 (??) or so, with Ken Schuggert (?) as the pilot? His prop was stalled up to about 50 kts(?), idling down the runway (because it would make more thrust idling than at rpm), until it started to bite..
Long take-off roll, but would go like stink once at speed.
For a CH-801, speed is of no concern, acceleration is everything - static thrust IS getting interesting here!
 
I assume as a dyno it would be interesting to have a special static prop to load the engine and eventually it can be used to compare engines/mods/etc. with this one prop as a baseline. Whether this dyno prop has any aviation use at all doesn't matter, it puts some serious load on the engine. How to calibrate this prop is a different question, but just to see, whether an engine runs better or worse than before it is good enough....

""""snip"

Ok... I've seen countless little red biplanes hang from their prop at airshows; certainly the prop is "stalled", and knowing that the engine/prop combination can produce thrust to counter the gross weight in order to allow the plane to hover is useful information to this small group of pilots. But how many of us really need that info?

 

"""snip"
 
If that prop is stalled the bird comes down!! Just because the plane has zero speed, does not mean the prop is stalled.
In this case it rather works like a inefficient, but effective rotor, vertical inflow speed should be rather impressive.
 
If you observe: Non of these stunts starts with a standing motor - they always pull up and slowly reduce speed and adjust rpm/pitch. At this point a inflow inertia gets established ( I guess it takes about 1-3 seconds, wild guess from helo experience) and kept there with excess power. I don't know how close they are to a real stall - but at this moment they are NOT stalled. You would hear the engine overspeed and the plane accelerate tailwards!! :))
 
TJ

 
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