Jump to content
  • Welcome to Recreational Flying!
    A compelling community experience for all aviators
    Intuitive, Social, Engaging...Registration is FREE.
    Register Log in

Recommended Posts

Posted (edited)

Looks to me, from the witness description, very much like an unrecoverable stall at low altitude, whilst banking.

It seems so many pilots neglect to watch airspeed when travelling low and slow, and looking for terrain features or terrain recognition.

 

There is also an unexplained control-issue event involving another Liberty XL-2 in 2015, at Camden.

Might be the Liberty has some "issues" as regards handling?

 

https://www.atsb.gov.au/media/5750261/AO-2015-125 Final.pdf

Edited by onetrack

Share this post


Link to post
Share on other sites

I have heard stories that the Liberty's are known to 'bite', and looking at the thin, almost laminar wing, I would tend to agree.

That said, I've never flown one so who knows, could well be a pussycat.

Share this post


Link to post
Share on other sites

The newest photo in the news story shows an aircraft that has crashed in the classic flat spin crash position, not a nose dive.

 

The aircraft may be highly susceptible to relatively small CoG shifts, with a rearwards CoG shift, quite often behind a flat spin crash.

 

Or the Liberty may be similar to the Lockheed Hudson, which one test pilot warned, was, "not a machine for the careless or the ham fisted".

 

The Hudson design engineers in the 1930's, had settled on a highly-loaded wing of relatively small span and area, to enable much higher cruise speeds.

The Hudson wing had to utilise Fowler flaps to reduce landing and takeoff speeds to acceptable levels.

 

The Hudson wing also incorporated wing slots located just behind the leading edge, which slots were reputed to prevent stalls, below normal stall speeds.

But they didn't, the slots only led to an abrupt wing stall characteristic on the Hudson, due to the highly loaded wing design.

This characteristic caught out a lot of new pilots with slow reflexes, with the all-too-common Hudson sudden stall, and resultant crash.

  • Like 1

Share this post


Link to post
Share on other sites

  The Hudson was just the first of many  more complex flapped planes. Just look a the  wing of the jetliner you fly in when it's set up for landing, and they need quite a bit of power on the approach to overcome the extra drag associated with the extra lift.. Nev

  • Like 1

Share this post


Link to post
Share on other sites
On ‎6‎/‎08‎/‎2019 at 1:12 PM, onetrack said:

ooks to me, from the witness description, very much like an unrecoverable stall at low altitude, whilst banking.

It seems so many pilots neglect to watch airspeed when travelling low and slow, and looking for terrain features or terrain recognition.

 

True, but the telling factor is in how much the wing is loaded up during turns. At lower IAS, and lowish heights above terrain - it's vital that power is increased before/as the turn is initiated. This increases lift, and avoids increasing angle of attack to prevent height loss in the turn. It varies from type to type, but more often than not, too much flap is used for lower level flight. This uses up extra power, which could have been used to improve the turn safety.  Sure, flap reduces Vs, but not so much that you can ignore the negating effect of the extra drag due the flap extension.

 

Before allowing the aircraft to descend to 'low' level, it should have been trimmed to the target speed that you consider, or the POH says, is recommended for slow flight. After this, all the pilot needs to do is vary power settings to cause the nose to fall, or rise - or the IAS to be increased into turns. Makes all the difference if your head is 'out the window' and there are no inside distractions.

 

The other factor in these lower level/lower speed turns is whether the ball is precisely in the centre. Too many pilots are guilty of trying to increase the rate of turn by pushing in too much rudder, (usually in LH turns), causing a skidding turn. This is a surefire way to stall the inside wing and spin under. Recovery takes thousands, not hundreds, of feet altitude. Nothing really dangerous about a steeper turn with power, which many pilots are afraid of at lower level. The laws of aerodynamics apply just as truly at 300ft agl as at 3000ft.

 

 

  • Like 1
  • Agree 2
  • Informative 1
  • Winner 1

Share this post


Link to post
Share on other sites

But in training, we are taught to "keep the plane from losing height", when doing our "coordinated turns",

spacesailor

 

 

Share this post


Link to post
Share on other sites

But "in training" one might also be advised to unload the wing whenever necessary or desirable. As in:

 

 

 

  • Like 2
  • Agree 2

Share this post


Link to post
Share on other sites

  Keep to one side to preserve maximum room for the turn. Usually the RHS for side by side cockpits.. Be ready for the need for one any time you are going UP a valley. You don't want the nose to drop too far in such a manoeuver either. Review thoroughly Spiral and Spin recovery differences. If you get into  a spiral you must react quickly or you will lose a lot of height and get too fast with your nose pointing at the ground.. One early situation that killed pilots was called the graveyard SPIRAL (not misnamed). Nev

Share this post


Link to post
Share on other sites
3 hours ago, Garfly said:

But "in training" one might also be advised to unload the wing whenever necessary or desirable. As in:

 

Good advice:the imperative is not to load up the wing when you have altitude below you in the centre of the valley. 20 deg flap and 60-65 KIAS is right on the edge for an unmodified C182. NB: the demo here was done with a C182 fitted with a Sportsman STOL kit - which is a step upwards in lower speed flight. For the average pilot in a 172, 182 type - use 65-70KIAS and 15-20 deg flap.  Note also that as the nose was allowed to fall away in the late stages of the 180 turn - the IAS rapidly increased from 60 to 80. But, still within the white arc.  Without flap being deployed, expect this to be faster again. Of course, this demo was done in clear skies - it looks a whole lot different if you are doing it under a cloud base with rain along the mountains.

PNG highlands strip and Cessna 185 (2).jpg
  • Informative 1

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later for your post to be seen If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...