lml@lancaironline.net Mailing List Archive

Posted for Terrence O'Neill <troneill@charter.net>:

Jeff,

Interesting Australian TSB report.  I might offer one observation:
Here an aircraft included an AOA of a type which showed stall, in terms of
speed being calibrated for 1G.  The report refers to stall in terms of speeds.
I note that this was a pressure-differential-type AOA, which I think does not
offer the pilot any information as to how many degrees the wing is at above
the wing's stall angle to the relative wind ... so that the report's reference
to a deck or horizon angle is meaningless.  A vane-type AOA instrument reading
out in degrees which would give the pilot an idea of how much he had to pitch
down to unstall the wing, would be informative to pilots ... for example, as
in the unfortunate AirBus airliner crash where the three high-time pilots held
the wing at a stalled angle all the way down to the ocean, complaining on the
recording in the black box that they 'did not undertstand what was happening'.
What does that tell us?
Terrence

[Not true... the AOA Pro has a digital readout at the bottom of the display that shows angle of attack to the 10th of a degree. While the Sport model is just a series of lights, its operation is the same. While it doesn't have an angular readout the display goes from the AOA when the wing is making zero lift (pressures equal top & bottom of wing, determined with zero-G maneuver during calibration... there would be no lights illuminated on the display at this point) to the AOA at which the wing stalls (all the lights on & bitchin' Betty going nuts). Transition from top yellow light to bottom red light happens at the airspeed 15% above the stall speed, regardless of CG, temp, gross weight, angle of bank, time of day, etc. SInce the wing will always stall at the same AOA (somewhere around 16-17 degrees) that means that the red light comes on around 12 degrees. I would imagine someone with a PRO could give the exact number, as the relationship is the same on it, with transition from yellow to red at 15% above stall speed, again, which always happens at the same AOA. I hope this clears up that misunderstanding.

<marv> ]

On Jan 8, 2013, at 10:25 AM, vtailjeff@aol.com wrote:

> For a good read see the following accident report from the Australian
>Transport Safety Board on a LIVP turbine accident. Be sure to read the
>analysis.
>
>
> http://www.atsb.gov.au/publications/investigation_reports/2002/aair/aair200206005.aspx
>
> Jeff
>
> -----Original Message-----
> From: Ron Galbraith <cfi@instructor.net>
> To: lml <lml@lancaironline.net>
> Sent: Tue, Jan 8, 2013 8:32 am
> Subject: [LML] Re: Stalls & Spins
>
> There is an ES video that shows what happens when you stall an ES at full aft
>CG.  Spins immediately, takes 2.5 turns and 3000' to recover.  Test Pilot was
>one turn from bailing out.   Install an AOA system, install stall strips,
>practice flying at low speeds and learn what impending stalls feel like. The
>airframe gives you many indications that you are too slow.  Learn them.  Fly
>safe.
>
> Ron
>
> Sent from my iPhone
>
> On Jan 8, 2013, at 8:34 AM, George Wehrung <gw5@me.com> wrote:
>
>> John,
>>
>> I would be interested in watching some of the videos on the ES in particular
>>if not the other airframes. Are they posted on the Internet by chance,
>>doubtful but I thought I'd ask.
>>
>>
>>
>>
>> Sent from my iPhone
>>
>> On Jan 8, 2013, at 15:50, John Smith <john@jjts.net.au> wrote:
>>
>>> From my perspective, the key phrase is spin resistance.
>>>
>>> Having researched the NASA material and having also seen the Lancair videos
>>>of actual flight testing, rightly or wrongly, I installed the wing cuffs to
>>>the Legacy on the basis that they seemed to offer the opportunity to make it
>>>harder to get into trouble, but accepting that if pushed too far into a spin,
>>>then the aircraft may or may not be recoverable. So, if one accepts the view
>>>of many which is that "as was", the aircraft was not spin recoverable, there
>>>would only appear to be upside from installing the cuffs. The flaw is, of
>>>course, that if indeed the Legacy is spin recoverable without wing cuffs, then
>>>the addition of the wing cuffs may preclude spin recovery!
>>>
>>> Unless someone goes to the trouble of spin testing the Legacy, or any other
>>>type fitted with cuffs, one will never know whether spin recoveries are
>>>possible under what flight and loading circumstances and, of course, with or
>>>without wing cuffs.
>>>
>>> Meanwhile, per my prior post on this, all I can say is that the albeit very
>>>limited flight testing (straight and level, and continuous 30deg AoB turns) in
>>>my Legacy fitted with the cuffs shows that there is plenty of warning of the
>>>impending stall – stall strips give the first "gentle" warning", followed by
>>>the more severe intermittent "shuddering" as the centre section drops in and
>>>out of the stall (whilst the outboard sections are still flying).
>>>
>>> I'm happy to talk to anyone if they are interested to talk about this more….
>>>numbers below, but please note time is UTC + 8!!
>>>
>>>
>>> Regards,
>>>
>>> John
>>>
>>>
>>> John N G Smith
>>> Tel / fax:    +61-8-9385-8891
>>> Mobile:      +61-409-372-975
>>> Email:         john@jjts.net.au
>>>
>>>
>>> From: <marv@lancair.net>
>>> Reply-To: Lancair Mailing List <lml@lancaironline.net>
>>> Date: Tuesday, 8 January 2013 2:25 AM
>>> To: <lml>
>>> Subject: [LML] Re: Stalls & Spins
>>>
>>>
>>>
>>> Posted for "Peter Field" <pfield.avn@gmail.com>:
>>>
>>> Dear Lancair Drivers:
>>>
>>>
>>>
>>> I've been following the discussion on stalls and spins and I want to add
>>> some additional factual information purely for your personal consumption and
>>> reflection.  Attached are excerpts from 10 different 1980-90 NASA flight
>>> test final reports on a series of GA airplanes in which NASA evaluated the
>>> use of cuffs on leading edges to improve the behavior of the test airplane
>>> approaching the stall.  For various reasons the cuffs improved lateral
>>> control entering the stall, but had the adverse effect of destabilizing the
>>> aircraft once a fully developed spin was achieved.  Essentially, stall
>>> behavior was improved at the sacrifice of spin recovery.  Cuffs on wing
>>> leading edges are an add on design fix, the more elegant solution is
>>> "washout," where the wing is twisted so the outer portions of the wing
>>> always operate at a lower angle of attack.
>>>
>>>
>>>
>>> To my knowledge, Lancair has never subjected any of their aircraft to a
>>> fully developed spin matrix complete with appropriate instrumentation and a
>>> spin recovery chute.  There is no FAA requirement for them to do so - it's
>>> an Experimental Category airplane.  Early on they may have lightly touched
>>> on such testing; but I have never seen any documentation on a fully
>>> completed spin matrix, which would involve at least 160 spins at various
>>> cg's and lateral loadings.  In my opinion, it would be highly risky to fool
>>> around much beyond the stall in any Lancair - there is no documentation that
>>> indicates any of these airplanes can always be recovered from a one turn
>>> incipient phase spin or any fully developed spin.  Being good at spin
>>> recovery isn't so much a matter of how skillful a pilot you are, it's a
>>> matter of how many spins you've experienced in airplanes known to be
>>> recoverable.  Being familiar with the stall characteristics of your own
>>> airplane should be a matter of personal preference.
>>>
>>>
>>>
>>> Best regards,
>>>
>>> Pete Field (LNC2)
>>>
>>> USNTPS graduate & spin recovery instructor
>>>
>>>
>>>
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