Surely it depends on how much G you are pulling (or not)??
Willie Harrison
G-BZNY
>-- Original Message --
>To: europa-list@matronics.com
>From: Andrew Sarangan <asarangan@yahoo.com>
>Date: Wed, 2 Aug 2006 07:13:54 -0700 (PDT)
>Subject: Re: Europa-List: Re: stalls & spins
>Reply-To: europa-list@matronics.com
>
>
>I don't see the ASI and the AOA as entirely different things, especialy
>in a small GA cockpit. The ASI can be calibrated to read angles instead
>of speed based on aircraft weight, like the movable outer ring that is
>used for calibrating TAS based on temperature. A true AOA independent
>of weight is useful only in large transport aircraft where the weight
>could vary significantly.
>
>
>--- Mark Burton <markb@ordern.com> wrote:
>
>>
>> Folks,
>>
>>
>> graham@gflight.f9.co.u wrote:
>> >
>> > Mike will have a much more valid opinion than me but I believe the
>> > sensible way to monitor airspeed is by angle of attack, the
>> instrument
>> > tells that that your airspeed is going to change, you can correct
>> the
>> > changed AoA instantly and speed won't change The ASI tells you at
>> least
>> > 20 seconds after it's changed which means you then have to regain
>> > momentum which will take another 20 seconds or more. Another
>> advantage
>> > that correct AoA is not dependant on weight, so the figure for
>> stall,
>> > cruise max range etc all remain constant.
>> > my 2 cents
>> > Graham
>> >
>>
>>
>> There is much good information in Graham's message but I feel that
>> this last paragraph is misleading. Unless your ASI is particularly
>> sluggish, it will indicate changes in airspeed almost instantly (i.e.
>> not 20 seconds later). What takes the time is actually changing the
>> speed of the aircraft relative to the surrounding air. Fitting an
>> AoA gauge does not make your aircraft accelerate any quicker!
>>
>> Let's imagine the situation where you are on approach and your
>> airspeed is a little below the optimum speed (the AoA is higher than
>> desired). Assuming you are not too low, you lower the nose to
>> increase the speed (and reduce the AoA). As soon as the nose is
>> lowered, the AoA will decrease and if you have an AoA gauge that will
>> be indicated immediately. The airspeed, however, does not change
>> straightaway (the ASI lag!!!) After a while, your airspeed will
>> settle at the new increased value. (perhaps a kind aerodynamics
>> person can provide us with a succinct description of what causes the
>> airspeed to increase when the AoA is reduced).
>>
>> Moving the stick forward to reduce the AoA is the crucial action.
>> Having moved the stick, the pilot then has to wait until the speed
>> stabilises before sampling the ASI again (all gliding instructors
>> will remember giving this demo). If the speed doesn't have to change
>> by very much (say, < 5 kts) then the pilot doesn't have to wait very
>> long (certainly less than 20S).
>>
>> The rational behind the talking ASI is that if the airspeed on
>> approach is not far from the desired speed, then the pitch/throttle
>> adjustments required to return to that speed are small and the time
>> lag between making an adjustment and achieving the desired speed is
>> small. The pilot is "nagged" into maintaining the correct airspeed
>> through small changes in pitch/power.
>>
>> By nagging the pilot to maintain a sensible speed, the talking ASI
>> not only protects against stalling, it helps you obtain the
>> stabilised approach that Mike Parkin enthused about and is so
>> important when operating out of small fields.
>>
>> I understand the benefits of flying by AoA and if someone produced a
>> low cost, reliable, easy to fit and calibrate, AoA instrument that
>> didn't require you to have your eyes in the cockpit on approach, I
>> would be tempted to have one.
>>
>> Mark
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?p=51717#51717
>>
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