Tim et al,
Reflecting on your message, you may agree with me on a few points.
Pitch angle refers to the angle between the a/c longitudinal axis and level.
Angle of incidence, if not mistaken, to longitudinal axis and MAC(?)
The vanes in front of the Jaguar, I believe would measure AOA, which is rela
tive airflow to long. axis.
I do agree that measured AOA could be affected by proximity to the wing, but
isn't that the reason it is placed there, in order to read actual AOA on th
e wing and not theoretical?
Brgds and queuing up for correction :-)
Alex Kaarsberg
Em 11/05/2014, =C3-s 13:09, houlihan <houlihan@blueyonder.co.uk> escreveu:
> Hi Graham.
>
> I agree with your comments about the availability of AOA indications, I ha
ve not looked in depth at this but my understanding is the systems available
are both very expensive and difficult to install.
> During development of the Jaguar aircraft the test aircraft had vane senso
rs mounted well forward on the pitot boom these measured pitch and yaw and v
alidated the fuselage mounted incidence gauge. This was a fairly standard de
vice that had a tube with a pair of slots that rotates to equal the pressure
and aligns with the airflow
> On a single engined piston plane anything mounted on the fuselage will be a
ffected by propwash and other factors, if it is mounted on the wing then the
results will be affected by the wing itself and vortcies and flow breakdown
probably at critical phases of flight. how would you check if the installat
ion is sound and reports correctly without having carried out elaborate flig
ht testing first.
> I guess and its only a guess is that the pitot based versions are likely t
o have the same limitations as standard pitots with things like position err
or and other effects I expect these things are all able to be corrected out o
ne way or another with clever computation. Why is nothing simple ?
>
> I stand by to be corrected
>
> regards
>
> Tim
>
>
> On 11 May 2014 11:22, GRAHAM SINGLETON <grahamsingleton@btinternet.com> wr
ote:
> Tim
> maybe we are mixing things a bit. ASI will measure instantly changes in ai
rspeed.
> When AoA changes aircraft speed will not change instantly but will take se
veral seconds.
> The force causing change of airspeed is increase or decrease in drag, usua
lly quite a small force.
> During take off acceleration is caused by engine thrust and ASI will recor
d speed of course, as soon
> as the aircraft is flying AoA should quickly settle at best climb.
> Stall occurs at the same AoA whatever airspeed or total weight is. (I'm th
inking aloud here)
> In fact best climb, cruise or glide speeds are also at fixed AoAs. They ar
e not at fixed airspeeds but
> change as all up weight changes.
> AoA is much the best primary flight control instrument. That's why fast je
ts use it.
> A pity AoA meters aren't mass produced like ASIs are!
> best regards
> Graham
>
>
> From: houlihan <houlihan@blueyonder.co.uk>
> To: europa-list@matronics.com
> Sent: Sunday, 11 May 2014, 8:34
> Subject: Europa-List: Re: Europa-List: Re: Europa-List: Re: Europa-List: R
e: Europa-List: Europa Crash in L=C3=BCbeck/Germany
>
> Hi Graham.
>
> We may be talking apples against pears here BUT if what you say is true th
en on takeoff I would be at 100' thinking about retracting the undercarriage
before the ASI has moved from zero.
>
> I agree it takes time to accelerate or decelerate a 600kg mass but the pre
ssure measurement showing movement relative to the local air mass will be in
dicated within a small fraction of a second even using our normal mechanical
manometers that are calibrated in airspeed and could be even quicker using e
lectronic pressure sensors close to the pitot head.
>
> True an AOA or alpha system would be helpful but I just want to be warned i
f through lack of attention or being distracted I allow my speed to decay , t
hese lack of attention or distraction events usually build up slowly without
it being noticed and I would guess rarely happens over one or two seconds.
>
> best regards
>
> Tim
>
>
> On 10 May 2014 22:28, GRAHAM SINGLETON <grahamsingleton@btinternet.com> wr
ote:
> Tim
> don't think so , the ASI won't move (or shouldn't!) until the aircraft has
accelerated, or worse slowed down and that takes many seconds.
> When it says "stall speed!" you.ve already stalled. Not a lot of use.
> Graham
>
>
> From: houlihan <houlihan@blueyonder.co.uk>
> To: europa-list@matronics.com
> Sent: Saturday, 10 May 2014, 14:31
> Subject: Europa-List: Re: Europa-List: Re: Europa-List: Europa Crash in L=C3
=BCbeck/Germany
>
> Hi Graham.
>
> I think you may have put the decimal point in the wrong place. I appreciat
e what you are suggesting but 20 seconds ?
> I bet the real figure is much less than a second.
> Mind you how would you measure the lag , my ASI seems to move at the speed
of light at times.
>
> Tim
>
>
>
> On 10 May 2014 13:19, GRAHAM SINGLETON <grahamsingleton@btinternet.com> wr
ote:
> Or an AoA meter as primary attitude/speed instrument. The ASI is always 20
seconds too late.
> Very sad, I met Manfred while he was building. A very nice man and a nice E
uropa.
> Graham
>
>
> From: David Joyce <davidjoyce@doctors.org.uk>
> To: europa-list@matronics.com
> Sent: Saturday, 10 May 2014, 12:36
> Subject: Re: Europa-List: Europa Crash in L=C3=BCbeck/Germany
>
k>
>
>
> I strongly suspect that this another case where a SmartASS or the equivale
nt might have saved them both. David Joyce, G-XSDJ
>
>
>
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