Never exceed speed

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Postby lazflyn » Tue Oct 28, 2003 6:12 am

I was browsing the Lazair Force web site and read something I now wonder about. I was reading the old brochure from Ultraflight. It stated that the never exceed speed was 55 mph. Is that really true? Anyone ever gone past that? I would think that Lazairs with upgraded engines and enclosures breeze right past that. I seem to remember going 60 once, now that I think about it, in a cruise descent. I remember thinking: I wonder what the Vne is for this sweet little airplane. Does anyone know?

MarkDJ :unsure:

p.s. I have a pic of me flying a Lazair. How do I post it?
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Postby lazair » Tue Oct 28, 2003 9:10 am

VNE
2 seater 62 mph
ser III 55 mph
SS 65 mph
Elite 65 mph

quoted from Lazair Manual
Lazair was Lazy in the AIR.
Designed for low and slow flight. It like power it up like a 1/4 mile dragster and get to vne or cruise faster and shorten takeoff roll. But you still have a high lift wing that will be more drag the faster it goes.

Lazair


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Postby lazairkid » Tue Oct 28, 2003 2:54 pm

QUOTE (lazflyn @ Oct 28 2003, 07:12 AM)
I was browsing the Lazair Force web site and read something I now wonder about. I was reading the old brochure from Ultraflight. It stated that the never exceed speed was 55 mph. Is that really true? Anyone ever gone past that? I would think that Lazairs with upgraded engines and enclosures breeze right past that. I seem to remember going 60 once, now that I think about it, in a cruise descent. I remember thinking: I wonder what the Vne is for this sweet little airplane. Does anyone know?

MarkDJ :unsure:

p.s. I have a pic of me flying a Lazair. How do I post it?

:blink: Mark, DJ
What I have is this. The Lazair-3 Vne was 55 mph
The Lazair SS & Elite was 65 mph
And the 2-seat was 62 mph
This comes from the December 83 Lettair News letter.
The Lettair was a news letter that ultraflight put out
to update Lazair pilots in on what was going on with the Company and plane.
I have heard of pilots going 70 mph in a dive with no
affect to the wings, but I don't recommend it.
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Postby Scot » Wed Nov 12, 2003 8:21 am

With regards to questioning the VNE. Any airplane can breeze past it's VNE in variable attitudes. I think that a 20 year old lazair, could probably reach oh ..... 80 or 90 before the wing decided to rip in half or folded. The VNE is obviously designed with a safety margin so that when people ACCIDENTLY exceed it, they don't instantly become a statistic. Anyone can make an error in judgement while flying, but I wouldn't recommend making a habit of it. The wing deformation and resultant stretching and contracting of the aluminum is going to cause a crystalization of molecules that will not necessarily show up the first few times that it is done, but will definitely weaken that structure that keeps you defying the laws of gravity. It's a cumulative thing, where nobody really knows how many times their PREVIOUSLY OWNED wings, have already been stressed beyond acceptable limits.
My hope is that we all keep defying the laws if gravity and grave.... ity for many years to come !

>> Scot '-----x-/\-x-----'
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Postby lazair » Wed Nov 12, 2003 8:31 am

Scot,

This is why the larger engines are fine in moderation and for extra thrust in liftoff but your vne remains. Unless the entire Lazair is rebuilt i would not want to be flying the stressed wings over 60 to 70 mph. It is a slow speed high lift wing.


Just think of the frontal area on the d cell over 18 feet with the two little wing atttach tabs holding that force.

This is why any skin deformation on D- Cells is a warning sign to possble over stress from flying or accidents.

And yes you can only bend a beer can so many times unitl it breaks in two.


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Postby Tom Thomson » Sun Mar 14, 2004 6:45 pm

The published VNE for the Lazair may have something to do with FAR-103, the reg which governs ultralights in the US. It states that max, full power, level speed cannot exceed 55 knots.
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Postby lazair » Mon Mar 15, 2004 10:19 am

Hi Tom, And Welcome here.

Lazair was 55 mph not knots but i stand to be corrected.

Also who would want to fly at much more in "flying lawn chair" anyways ? :)

QUOTE
Posted on Oct 28 2003, 09:10 AM
--------------------------------------------------------------------------------
VNE
2 seater 62 mph
ser III 55 mph
SS 65 mph
Elite 65 mph

quoted from Lazair Manual
Lazair was Lazy in the AIR.
Designed for low and slow flight. It like power it up like a 1/4 mile dragster and get to vne or cruise faster and shorten takeoff roll. But you still have a high lift wing that will be more drag the faster it goes.

Lazair

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Postby ozzie » Tue Mar 16, 2004 3:02 am

Yes the speed was in MPH i have a read some where that the position of the hall asi on the early lazairs under read at the top end and then stopped moving at 55mph. the asi had to be moved futher out to avoid the effects from the props. when i fitted the extention i found that i was entering some manouveres at 65 mph indicated. so think about the position of your pitot for accurate readings.
The problem of having the power to cruise at or just below your vne is SHOCK LOADING. all aircraft have a turbulant air penatration speed if the wing is already highly loaded from driving it hard through the air flying into tubulance produced from any source can result in short sharp and very close and in some cases past the ultimate yeild of a componet or material in thousandths of a second. tubby pilots note shock loading goes up with weight. and anyway who says the wing will fail first?
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Postby lazair3ca » Tue Mar 16, 2004 11:32 am

Very interesting topic here. In some cases I thought the Vne was defined by flutter of the control surfaces. The surfaces on the Lazair are not balanced and any play due to wear or whatever will make the surfaces prone to flutter.
Has anyone experienced flutter and survived?
Bill
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