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-   -   Light aircraft down in Somerset (https://www.pprune.org/accidents-close-calls/570620-light-aircraft-down-somerset.html)

Genghis the Engineer 19th Nov 2015 17:58

Pull What - the much greater inertia of an airliner means that there is very much slower change in momentum due to changes in wind than the much lower inertia light aircraft.

Additionally, a piston engine can increase power almost instantaneously if required - say to counter a high rate of descent, whilst a turbine engine has a relatively large spool-up time.

G

Genghis the Engineer 19th Nov 2015 18:07


Originally Posted by Mixed Up (Post 9185545)
Could he not have had QNH set when he thought he had set QFE? He may have thought he was 800' AGL (and in cloud). When he saw the ground he may have pulled up hard and stalled into the ground.

The ground is about 800' AMSL there.

Such a tragedy for so many. I hope the AAIB report will report quickly.

If so, he was still at least 300ft below what he thought MSA was. And presumably any decent quality GPS would have been showing a terrain warning?

G

chevvron 19th Nov 2015 18:27


Originally Posted by rog747 (Post 9183152)

a complete tragedy - would his departure station Fairoaks not have given him as what seems a very novice pilot with a new plane some hint that its not a good idea to go or do they not have that remit to say anything???

Phil was not a novice pilot and he'd been flying that particular aircraft for a couple of years. I forget what he had before, it could have been a Cirrus.
Fairoaks AFIS would have given him a PIREP for the area if they'd had one, (although not compulsory) but given the weather, very few people were flying in the area that day to pass such a report.

rog747 20th Nov 2015 06:47

chevron
 
dear chevron

re your post
Phil was not a novice pilot and he'd been flying that particular aircraft for a couple of years. I forget what he had before, it could have been a Cirrus.
Fairoaks AFIS would have given him a PIREP for the area if they'd had one, (although not compulsory) but given the weather, very few people were flying in the area that day to pass such a report.

many thanks for that - i had no wish to appear defamatory to the poor chap - I assumed (quite wrongly from the press and his FB/twitter feed) that
he was maybe a newbie/novice --- apologies

Pull what 20th Nov 2015 09:44

GE

I think your logic is flawed- modern turbo jets spool up very quickly especialy at approach thrust and have much more excess thrust to get away from tbe shear besides the fact that the lower penetration speed of light aircraft makes them more prone to windshear effects.

A good article here

safety_llws

quote

Small, general aviation aircraft are much more prone to the effects of low-level wind shear than large commercial aircraft because their approach speeds are much closer to their stall speeds.

Having practiced windshear recovery in several jet sims including the Airbus I can assure you there is no way a light aircraft would have got through the same equivalent shear

Genghis the Engineer 22nd Nov 2015 07:28

Simulation and Analysis of Wind Shear Hazard.

At first check on literature PW, it appears that we may both be wrong - albeit not from very recent research.

G

N707ZS 22nd Nov 2015 11:41

Thought with turboprops you keep the power on and then pitch the blade back on approach, then if required you alter the blades and have the power to go-around, no need to spool up.

flapassym 23rd Nov 2015 06:52

Every turboprop I ever flew, we'd put the props to max rpm once on approach, the lower power setting kept the RPM down but in the event of a go around max RPM was immediately available. Same as any piston twin I ever flew as well.

BTW this was a Mirage not the Meridian and I think therefore was a piston engined variant.

Tragic nonetheless.

Pull what 9th Dec 2015 14:58


Windshear is primarily a large aeroplane problem, it's not generally significant in anything this light
.

GE -The quoted article is a mathematical model from 1977, hardly representative of modern thinking.

To say that windshear isnt generally significant on a light aircraft is quite frankly ridiculous. Windshear is significant to all aircraft and to suggest otherwise is irresponsible in my opinion

Genghis the Engineer 14th Dec 2015 16:10

I'm not aware that the basic principles of flight mechanics have changed since 1977, only the amount of computing power available if you want to model it.

In this instance, I opined that windshear primarily affected big aeroplanes, PW opined that it primarily affected smaller aeroplanes - whilst NASA said that it affects all aeroplanes with no particular distinction.

I think that even if they did say it in 1977, NASA probably have the deciding vote in that particular matter - but nobody actually said that windshear didn't affect anything.


That said, there's still no evidence I've seen that windshear conditions existed at the time and place of this accident.

G

punkalouver 16th Feb 2022 21:54

Just read the report. Sounds like someone flying VFR in very poor destination weather. Control of the aircraft was lost with large pitch up and pitch down maneuvers ending up in a final stall and spin. The possible initiating factor(which could not be conclusively established) was that an attempt was made to make a significant pitch control input, resulting in the trim operating in the opposite direction to maintain altitude, resulting in a significant out of trim situation in IMC.

Regardless of whether this was what actually happened, a good reminder on what can happen when trying to override the autopilot on some aircraft......
Piper_PA-46-350P_Malibu_Mirage_N186CB_11-16.pdf (publishing.service.gov.uk)

Timmy Tomkins 17th Feb 2022 13:20

An avoidable tragedy by the look of it. A day to stay at base or divert when destination was below sensible limits. Sadly not an uncommon problem


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