In wave, in blue hole at cloud level, hole closes, in IMC, then what?

On Saturday, April 11, 2015 at 2:31:02 PM UTC-7, Martin Gregorie wrote:
On Sat, 11 Apr 2015 11:34:01 -0700, Bob Pasker wrote:

On Saturday, April 11, 2015 at 12:02:23 AM UTC-4,
wrote:
"Its also worth mentioning that Vne is not based on load factor, like
Va, but on flutter, which is why its True and not Indicated. "

Actually flutter is dependent on equivalent airspeed not true airspeed.

VD is defined based on EAS (eg FAR 23.335), and Vne is defined based on
VD (23.1505).

But EAS doesn't take into account air density, which is primarily a
function of altitude (and a some temp thrown in). So Vne has to be
corrected for air density, which is the TAS.

Are you sure about that?

This reference says that EAS is a measure of dynamic pressure and gives
several formulae for it that all use either air density or air pressu

https://en.wikipedia.org/wiki/Equivalent_airspeed

Yes, I know about Wikipedia's dodgy treatment some social facts, but IME
its pretty good on this sort of stuff.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

I always thought IAS (or EAS minus instrument error) was just an indication of dynamic pressure, in fact that is how the instruments are constructed: to measure dynamic pressure. It is proportional to rho, air density.

On Saturday, April 11, 2015 at 6:15:16 PM UTC-7, jfitch wrote:
On Saturday, April 11, 2015 at 2:31:02 PM UTC-7, Martin Gregorie wrote:
On Sat, 11 Apr 2015 11:34:01 -0700, Bob Pasker wrote:

On Saturday, April 11, 2015 at 12:02:23 AM UTC-4,
wrote:
"Its also worth mentioning that Vne is not based on load factor, like
Va, but on flutter, which is why its True and not Indicated. "

Actually flutter is dependent on equivalent airspeed not true airspeed.

VD is defined based on EAS (eg FAR 23.335), and Vne is defined based on
VD (23.1505).

But EAS doesn't take into account air density, which is primarily a
function of altitude (and a some temp thrown in). So Vne has to be
corrected for air density, which is the TAS.

Are you sure about that?

This reference says that EAS is a measure of dynamic pressure and gives
several formulae for it that all use either air density or air pressu

https://en.wikipedia.org/wiki/Equivalent_airspeed

Yes, I know about Wikipedia's dodgy treatment some social facts, but IME
its pretty good on this sort of stuff.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

I always thought IAS (or EAS minus instrument error) was just an indication of dynamic pressure, in fact that is how the instruments are constructed: to measure dynamic pressure. It is proportional to rho, air density.

Here is the reference I think I was remembering. Can't seem to access it now without money, but the abstract pretty much says it. I think Schleicher at least believes this, or they would not have bothered to put mention and tables in their manuals.

http://journals.sfu.ca/ts/index.php/ts/article/view/216

On Sat, 11 Apr 2015 18:42:07 -0700, jfitch wrote:

I always thought IAS (or EAS minus instrument error) was just an
indication of dynamic pressure, in fact that is how the instruments are
constructed: to measure dynamic pressure. It is proportional to rho,
air density.

Here is the reference I think I was remembering. Can't seem to access it
now without money, but the abstract pretty much says it. I think
Schleicher at least believes this, or they would not have bothered to
put mention and tables in their manuals.

http://journals.sfu.ca/ts/index.php/ts/article/view/216

I first heard about the in-flight use of EAS in Feb, when Col. Richard
Graham (USAF, retd.) visited our club and gave a talk about flying the
SR-71, which was flown using EAS. Very interesting indeed: if you get the
change to hear him, do it.

We asked him if it would glide. Turns out that it would: flame-outs at
altitude had to be glided down to 30,000 before attempting a relight.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

A couple of points no one seems to have mentioned:

Vne on some types may be determined by pitch stability, not flutter speed,
and this is largely TAS related.

If you have been wave flying at height, in very cold air, and then you make
a rapid descent, and fly though a cloud layer below the freezing level on
the way down, you will get a frosted glass conopy, through which you can
see nothing, and it will take several minutes to clear. I once saw a very
experienced pilot, who had done this, land, brakes fully open, holding the
canopy partly open with one hand whilst he landed the glider using the
other hand.

At 07:18 12 April 2015, Martin Gregorie wrote:
On Sat, 11 Apr 2015 18:42:07 -0700, jfitch wrote:

I always thought IAS (or EAS minus instrument error) was just an
indication of dynamic pressure, in fact that is how the instruments
are
constructed: to measure dynamic pressure. It is proportional to rho,
air density.

Here is the reference I think I was remembering. Can't seem to access
it
now without money, but the abstract pretty much says it. I think
Schleicher at least believes this, or they would not have bothered to
put mention and tables in their manuals.

http://journals.sfu.ca/ts/index.php/ts/article/view/216

I first heard about the in-flight use of EAS in Feb, when Col. Richard
Graham (USAF, retd.) visited our club and gave a talk about flying the
SR-71, which was flown using EAS. Very interesting indeed: if you get the

change to hear him, do it.

We asked him if it would glide. Turns out that it would: flame-outs at
altitude had to be glided down to 30,000 before attempting a relight.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

VNE with altitude.

If your VNE changes with altitude, it will be listed in the glider's Manual, read it and quit trying to guess.

Todd Smith
3S

Interesting that you all talk about 'what to do' based on being caught in cloud on an unplanned basis. I fly with an A/H and am happy to thermal in cloud using that. However, I always worry about what to do if the A/H fails. My glider has no backup blind flying instrumentation (unlike most GA aircraft which have an electric turn coordinator as well as a vacuum horizon - and which are more speed stable than gliders).

My plan, tested in clear and admittedly smooth air, has been to open the air brakes and take hands and feet off if either the A/H shows obvious signs of failing or the airspeed increases over a certain level (I plan on 75 knots). A misleading A/H would be far worse than an obviously failed one, because you would be in worse shape before taking this action. However I recently talked to someone who had the A/H in his LX computer fail while in cloud.. He kept things steady while rebooting the LX and all was well. I think I would stick to the open the air brakes plan.

To answer (tongue in cheek) the original question......

"Stick your head between your knees, kiss your a$$ goodbye.......".

Unintended flight into IMC with a VFR aircraft (yes, basically regardless of type) is to be AVOIDED at all costs.
If it happens (you save it), "maybe" you'll save it and have a good story for the "I learned that from hanger flying" thread.........
You may also get to "test/wish you" had a chute if it comes out wrong. :-(

Weather is rather dynamic, if you're flying and it goes "bad", it's not a good place to be.

At 17:35 12 April 2015, waremark wrote:
Interesting that you all talk about 'what to do' based on being caught in
c=
loud on an unplanned basis. I fly with an A/H and am happy to thermal in
cl=
oud using that. However, I always worry about what to do if the A/H
fails.
=
My glider has no backup blind flying instrumentation (unlike most GA
aircra=
ft which have an electric turn coordinator as well as a vacuum horizon -
an=
d which are more speed stable than gliders).=20

My plan, tested in clear and admittedly smooth air, has been to open the
ai=
r brakes and take hands and feet off if either the A/H shows obvious
signs
=
of failing or the airspeed increases over a certain level (I plan on 75
kno=
ts). A misleading A/H would be far worse than an obviously failed one,
beca=
use you would be in worse shape before taking this action. However I
recent=
ly talked to someone who had the A/H in his LX computer fail while in
cloud=
.. He kept things steady while rebooting the LX and all was well. I think
I
=
would stick to the open the air brakes plan.



Sorry for the thread drift
One of my gliding club members in England was wave soaring over the
pennies when he lost lift ,and in to the cloud he went .
He switch his LX to horizon and made a safe decent ,but lost positional
awareness,he did not hit the hillside but at about 200ft it's fair to say
the
ground found him and a 6 month old asw31 would never be the same again .
He was not hurt but it took 3hours to walk off the hill and the retrieve is
was
a story all of its own and lasting over a week.
So the story is not over when you clear the bottom of cloud ,personally the

nearest I have been to a problem is descending through a closing hole only
to
find the canopy iced over ,but I managed to hang on until it melted and I
landed in a farmers field.As it was Christmas and my friends arrived with
the
trailer and bottles of wine he was very good with us and I put it down as I

learned from that and with the massive endorphin surge I had a great
Christmas.

Do you know why the 31 pilot did not use the engine to fly to an area where the cloudbase was higher?

I am not sure it won't be the same again! I think the UK agent bought the wreckage and is rebuilding it.

The SR-71 did have an what was refer to as an"unstart" where usually just one engine would flame out. This aircraft was one of the most amazing aircraft ever designed and built. it was the first stealth aircraft. A great read is "Sled Driver"


I first heard about the in-flight use of EAS in Feb, when Col. Richard
Graham (USAF, retd.) visited our club and gave a talk about flying the
SR-71, which was flown using EAS. Very interesting indeed: if you get the
change to hear him, do it.

We asked him if it would glide. Turns out that it would: flame-outs at
altitude had to be glided down to 30,000 before attempting a relight.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |