SR- 71/ Blackbird lore

[Larry Dighera]

In his book," Sled Driver," SR-71/ Blackbird pilot Brian Shul writes:

I'll always remember a certain radio exchange that occurred one day as
Walt (my backseater) and I were screaming across Southern California
13 miles high. We were monitoring various radio transmissions from
other aircraft as we entered Los Angeles airspace.

Though they didn't really control us, they did monitor our movement
cross their scope. I heard a Cessna ask for a readout of its
groundspeed. "90 knots," Center replied.

Moments later, a Twin Beech required the same. "120 knots," Center
answered.

We weren't the only ones proud of our groundspeed that day as almost
instantly an F-18 smugly transmitted, "Ah, Center, Dusty 52 requests
groundspeed readout." There was a slight pause, then the response,
"525 knots on the ground, Dusty."

Another silent pause. As I was thinking to myself how ripe a situation
this was, I heard a familiar click of a radio transmission coming from
my backseater. It was at that precise moment I realized Walt and I had
become a real crew, for we were both thinking in unison.

"Center, Aspen 20, you got a groundspeed readout for us?"

There was a longer than normal pause.... "Aspen, I show 1,742 knots"

No further inquiries were heard on that frequency

++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++

In another famous SR-71 story, Los Angeles Center reported receiving
a request for clearance to FL 60 (60,000ft). The incredulous
controller, with some disdain in his voice, asked, "How do you plan to
get up to 60,000 feet?

The pilot (obviously a sled driver), responded, "We don't plan to go
up to it, we plan to go down to it." He was cleared...

++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++

--<space>

Irrational beliefs ultimately lead to irrational acts.
-- Larry Dighera,

[Nicodemus Telrenner]

I like that. Didnt know you guys referred to them as Sleds though. And
particular connotation?
"Larry Dighera" > wrote in message
...
>
>
> In his book," Sled Driver," SR-71/ Blackbird pilot Brian Shul writes:
>
> I'll always remember a certain radio exchange that occurred one day as
> Walt (my backseater) and I were screaming across Southern California
> 13 miles high. We were monitoring various radio transmissions from
> other aircraft as we entered Los Angeles airspace.
>
> Though they didn't really control us, they did monitor our movement
> cross their scope. I heard a Cessna ask for a readout of its
> groundspeed. "90 knots," Center replied.
>
> Moments later, a Twin Beech required the same. "120 knots," Center
> answered.
>
> We weren't the only ones proud of our groundspeed that day as almost
> instantly an F-18 smugly transmitted, "Ah, Center, Dusty 52 requests
> groundspeed readout." There was a slight pause, then the response,
> "525 knots on the ground, Dusty."
>
> Another silent pause. As I was thinking to myself how ripe a situation
> this was, I heard a familiar click of a radio transmission coming from
> my backseater. It was at that precise moment I realized Walt and I had
> become a real crew, for we were both thinking in unison.
>
> "Center, Aspen 20, you got a groundspeed readout for us?"
>
> There was a longer than normal pause.... "Aspen, I show 1,742 knots"
>
> No further inquiries were heard on that frequency
>
> ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++
>
> In another famous SR-71 story, Los Angeles Center reported receiving
> a request for clearance to FL 60 (60,000ft). The incredulous
> controller, with some disdain in his voice, asked, "How do you plan to
> get up to 60,000 feet?
>
> The pilot (obviously a sled driver), responded, "We don't plan to go
> up to it, we plan to go down to it." He was cleared...
>
> ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++
>
> --<space>
>
> Irrational beliefs ultimately lead to irrational acts.
> -- Larry Dighera,

[Marc Reeve]

Nicodemus Telrenner > wrote:

> I like that. Didnt know you guys referred to them as Sleds though. And
> particular connotation?

I always presumed as in the "Rocket Sled" that Col. Stapp rode to fame
and face-distorted glory...

-Marc
--
Marc Reeve
actual email address after removal of 4s & spaces is
c4m4r4a4m4a4n a4t c4r4u4z4i4o d4o4t c4o4m

[Billy Beck]

1972, Barksdale AFB:

A visiting SR-71 leaving the base was taking what seemed an
inordinately long time holding in position for takeoff. I was
standing in front of Base Ops amid a small group of people watching,
when someone said, "I wonder what's taking him so long."

Whereupon someone else cracked, "He's waiting on a landing
clearance at Nellis."


Billy

http://www.two--four.net/weblog.php

[Big G]

(Marc Reeve) wrote in news:1fyin86.1brigrr3cte24N%
:

Hmmh, come again Marc? about the 'Col Stapp' and face-distorted glory..'
whats that mean? I met and chatted with an SR71 driver once for about an
hour at Mildenhall, England. His face was disfigured from some kind of
burns incident, would that be the face-distortion you're talking about?
This guy knew his Blackbird very well indeed.


> Nicodemus Telrenner > wrote:
>
>> I like that. Didnt know you guys referred to them as Sleds though.
And
>> particular connotation?
>
> I always presumed as in the "Rocket Sled" that Col. Stapp rode to fame
> and face-distorted glory...
>
> -Marc



--
Smiling
‹(•¿•)›
Big 'G' > ' Better than a smoke or a cup of tea '
Sure you can mail me: GARETHLROBERTS at TALK21 dot COM
Just please... PLEASE Dont spam me !

[Stephen D. Poe]

Big G wrote:
>
> (Marc Reeve) wrote in news:1fyin86.1brigrr3cte24N%
> :
>
> Hmmh, come again Marc? about the 'Col Stapp' and face-distorted glory..'
> whats that mean? I met and chatted with an SR71 driver once for about an
> hour at Mildenhall, England. His face was disfigured from some kind of
> burns incident, would that be the face-distortion you're talking about?
> This guy knew his Blackbird very well indeed.

Col. John Stapp was a pioneer in the US in aerospace medical research.
His rocket sled research included a 48g deceleration, resulting in well
known (at least in the US) pictures of Col. Stapp's seriously
g-distorted face.

"During the interval from 1946 through 1958, Colonel Stapp pioneered in
research on the effects of mechanical force on living tissues. In the
course of these investigations, a quantitative stress analysis of the
human body to limits of voluntary tolerance of crash type impacts and
decelerations. These dynamic stress analyses, including 76 human
experiments with rocket sleds decelerated from aircraft crash
velocities, over 200 experiments with human volunteers on swings,
catapults and other decelerating devices, provide criteria for aircraft
and ground vehicle safety design; for tolerance limits of trajectories
of ejection seats and escape capsules for supersonic and hypersonic; and
basic data applicable to impact forces expected in space ballistic
flight.

Simultaneously, effects of windblast were studied, both by exposure of
volunteers on high speed rocket sleds and in jet aircraft flights with
canopy removed. As a volunteer for 29 of the rocket sled deceleration
and windblast experiments, Colonel Stapp sustained decelerations of 25 g
average and 40 g peaks during a stop in 1.4 seconds from a velocity of
632 miles per hour attained by a rocket sled in 1954, in the last
experiment of this series. Colonel Stapp has not sustained loss of
consciousness nor permanent disability from any of these experiments,
although he incurred two wrist fractures, rib fractures, retinal
hemorrhages and lesser injuries at various times. Establishment of human
tolerance limits to impact forces in the order of 10,000 lbs. for
durations of a quarter of a second or less, and findings on the
quantitative relationship of the rate on onset of mechanical force to
injurious and lethal effects were worth the hazard of these
experiments."
- http://www.wpafb.af.mil/museum/afp/afp1199.htm

The search "+stapp +rocket +sleds" prodices about 70 results and
provides lots more background for those interested.

Stephen

[TBBlakeley]

> I met and chatted with an SR71 driver once for about an
>hour at Mildenhall, England. His face was disfigured from some kind of
>burns incident, would that be the face-distortion you're talking about?

Marc was not speaking about Brian Shul as you might have thought...Brian did
sustain burns from a T-28 he was flying for Air America......Marc was talking
about John Stapp when he face was distorted during his deceleration tests on
the rocket sleds.


As to the pilots of the SR calling them sleds...this term actually came from
the U-2 drivers talking "down" in a teasing way about then SR's. A bunch of
the SR drivers still won't call them sleds.

[Leslie Swartz]

When I was a Crew Chief at Beale AFB in the late 70s, IIRC the word "Sled"
referred to the handling/flight characteristics . . . (short for "Bobsled"
very fast, no steering)


Steve Swartz


"Nicodemus Telrenner" > wrote in message
...
> I like that. Didnt know you guys referred to them as Sleds though. And
> particular connotation?
> "Larry Dighera" > wrote in message
> ...
> >
> >
> > In his book," Sled Driver," SR-71/ Blackbird pilot Brian Shul writes:
> >
> > I'll always remember a certain radio exchange that occurred one day as
> > Walt (my backseater) and I were screaming across Southern California
> > 13 miles high. We were monitoring various radio transmissions from
> > other aircraft as we entered Los Angeles airspace.
> >
> > Though they didn't really control us, they did monitor our movement
> > cross their scope. I heard a Cessna ask for a readout of its
> > groundspeed. "90 knots," Center replied.
> >
> > Moments later, a Twin Beech required the same. "120 knots," Center
> > answered.
> >
> > We weren't the only ones proud of our groundspeed that day as almost
> > instantly an F-18 smugly transmitted, "Ah, Center, Dusty 52 requests
> > groundspeed readout." There was a slight pause, then the response,
> > "525 knots on the ground, Dusty."
> >
> > Another silent pause. As I was thinking to myself how ripe a situation
> > this was, I heard a familiar click of a radio transmission coming from
> > my backseater. It was at that precise moment I realized Walt and I had
> > become a real crew, for we were both thinking in unison.
> >
> > "Center, Aspen 20, you got a groundspeed readout for us?"
> >
> > There was a longer than normal pause.... "Aspen, I show 1,742 knots"
> >
> > No further inquiries were heard on that frequency
> >
> > ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++
> >
> > In another famous SR-71 story, Los Angeles Center reported receiving
> > a request for clearance to FL 60 (60,000ft). The incredulous
> > controller, with some disdain in his voice, asked, "How do you plan to
> > get up to 60,000 feet?
> >
> > The pilot (obviously a sled driver), responded, "We don't plan to go
> > up to it, we plan to go down to it." He was cleared...
> >
> > ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++
> >
> > --<space>
> >
> > Irrational beliefs ultimately lead to irrational acts.
> > -- Larry Dighera,
>
>

[RobbelothE]

I'm still amazed at the New York to London record set September 1, 1974: 1
hour 54 minutes and 56.4 seconds with an average speed of 1,807 statute mph
over the 3,461 statute mile distance (and that INCLUDES slowing down for a
refueling over the Atlantic)!!!!!!!


Ed
"Those who have long enjoyed such privileges as we enjoy forget in time that
men have died to win them."

Franklin D. Roosevelt, Address for Bill of Rights Day
15 Dec 1941

(Delete text after dot com for e-mail reply.)

[John]

Richard Caldwell wrote:

> As long as you guys are swapping lies about the Blackbird, would someone
> please recount the story of the SR-71 that suffered a flamout just this side
> of Africa on its way back to the east coast. As I understand it, that makes
> the SR-71 the record holder for long-distance gliding (as in un-powered
> flight). Of course, it could be just another whopper, but I've never gotten
> the "real poop" on that particular incident.
>
> Richard Caldwell

IIRC: That was a U-2 and he flamed out near Bermuda..
huge difference in the glide ratio of SR-71 & U-2

[Leslie Swartz]

Trust me, if anyone ever broke that record the SR would have easily
re-established a higher record . . .

The original record "upper limit" was set "low" to mask the true
capabilities of the aircraft.

Steve Swartz


"RobbelothE" > wrote in message
...
> I'm still amazed at the New York to London record set September 1, 1974:
1
> hour 54 minutes and 56.4 seconds with an average speed of 1,807 statute
mph
> over the 3,461 statute mile distance (and that INCLUDES slowing down for a
> refueling over the Atlantic)!!!!!!!
>
>
> Ed
> "Those who have long enjoyed such privileges as we enjoy forget in time
that
> men have died to win them."
>
> Franklin D. Roosevelt, Address for Bill of Rights Day
> 15 Dec 1941
>
> (Delete text after dot com for e-mail reply.)

[B2431]

>
>Trust me, if anyone ever broke that record the SR would have easily
>re-established a higher record . . .
>
>The original record "upper limit" was set "low" to mask the true
>capabilities of the aircraft.
>
>Steve Swartz
>

With all the radar and stuff like that there why are the capabilities of the
SR-71 still classified. I'm sure the bad guys already know. I'd really like to
know how high and how fast it realy was.

Dan, U. S. Air Force, retired

[RobbelothE]

>Subject: Re: SR- 71/ Blackbird lore
>From: John
>Date: 7/23/2003 9:01 PM Central Daylight Time
>Message-id: >
>
>Richard Caldwell wrote:
>
>> As long as you guys are swapping lies about the Blackbird, would someone
>> please recount the story of the SR-71 that suffered a flamout just this
>side
>> of Africa on its way back to the east coast. As I understand it, that
>makes
>> the SR-71 the record holder for long-distance gliding (as in un-powered
>> flight). Of course, it could be just another whopper, but I've never
>gotten
>> the "real poop" on that particular incident.
>>
>> Richard Caldwell
>
>IIRC: That was a U-2 and he flamed out near Bermuda..
>huge difference in the glide ratio of SR-71 & U-2
>
>

Yep. Like the difference between a lead-covered high drag rock and a feather.
Ed
"Those who have long enjoyed such privileges as we enjoy forget in time that
men have died to win them."

Franklin D. Roosevelt, Address for Bill of Rights Day
15 Dec 1941

(Delete text after dot com for e-mail reply.)

[Scott Ferrin]

On 24 Jul 2003 18:59:04 GMT, (B2431) wrote:

>>
>>Trust me, if anyone ever broke that record the SR would have easily
>>re-established a higher record . . .
>>
>>The original record "upper limit" was set "low" to mask the true
>>capabilities of the aircraft.
>>
>>Steve Swartz
>>
>
>With all the radar and stuff like that there why are the capabilities of the
>SR-71 still classified. I'm sure the bad guys already know. I'd really like to
>know how high and how fast it realy was.
>
>Dan, U. S. Air Force, retired


According to Wings of Fame Volume 9 pg 36 at one point in the program
the A-12 had reached Mach 3.56 and 96,200 ft.

Someone a while back posted a link to an image that listed 500 KEAS
(Knots ? AirSpeed) and somebody else mentioned 600 KIAS as the
structural limit. The aformentioned graph lists Mach 3.3 at about
seventy-two thousand feet as 440 KEAS. So if you extrapolate and
figure out what groundspeed five or six hundred knots IAS is at
96,000ft. . .who knows? Of course there are heat limits too in
there.

[vincent p. norris]

>>huge difference in the glide ratio of SR-71 & U-2
>
>Yep. Like the difference between a lead-covered high drag rock and a feather.

Well, in view of its speed, I doubt the SR-71 had high drag. I'd like
to hear what Mary Shafer has to say about that.

And "lead-covered...rock" seems to imply you think weight affects
glide ratio. It does not.

A U-2 constructed of lead would have the same glide ratio as one
constructed of balsa wood. It would glide faster, but just as far.

vince norris

[Dav1936531]

>From: vincent p. norris
>
>
>And "lead-covered...rock" seems to imply you think weight affects
>glide ratio. It does not.
>
>A U-2 constructed of lead would have the same glide ratio as one
>constructed of balsa wood. It would glide faster, but just as far.
>vince norris

Say what?
Dave

[B2431]

>>A U-2 constructed of lead would have the same glide ratio as one
>>constructed of balsa wood. It would glide faster, but just as far.
>>vince norris
>
>Say what?
>Dave

Um, I think there's be a slight difference in wing loading which just might
have a minor affect on glide ratio. Translation: the lead U-2 would glide like
a bowling ball.

Dan, U. S. Air Force, retired

[Keith Willshaw]

"Jack G" > wrote in message
...
> Only in a vacuum would both "glide" at the same speed and go the same
> distance - I think.
> Jack
>
>

In this case you are probably right but there is some truth in the
assertion.

Neglecting supersonic/transonic effects glide ratio is not effected by wing
loading but the glide speed is. This is why we find that large airliners
can have glide ratios comparable with many low performance
sailplanes. The difference being that their best glide speed is probably
an order of magnitude higher and so therefore is their rate of descent.

In the case of a lead U-2 though I imagine that glide speed would be
hypersonic :)

Keith

[Jim]

On 28 Jul 2003 20:43:34 GMT, (B2431) wrote:

>>>A U-2 constructed of lead would have the same glide ratio as one
>>>constructed of balsa wood. It would glide faster, but just as far.
>>>vince norris
>>
>>Say what?
>>Dave
>
>Um, I think there's be a slight difference in wing loading which just might
>have a minor affect on glide ratio. Translation: the lead U-2 would glide like
>a bowling ball.
>
>Dan, U. S. Air Force, retired

What a wonderful question. Glider pilots often add water ballast, 200
- 300 lbs I think, to their gliders to increase airspeed at a GIVEN
glide angle, thus improving the glider's penetration through the air
at that glide angle. The extra weight does not alter the glide angle
(except for very small improvements due to higher Reynolds numbers at
the higher airspeed). The glider's descent rate is increased by the
extra weight, but the airspeed is also equivalently increased so the
glide angle remains (pretty nearly) constant, glide angle being a
factor of only lift and drag, weight not even being in the
calculation.

As for a lead U-2 vs a balsa wood U-2, the lead U-2 would certainly
glide as long as its wing loading was such that its wing could supply
sufficient lift to sustain equilibrium in steady flight. The "catch"
here is probably the inclination to picture the lead U-2 and the balsa
U-2 as the same size. In such a case, if the lead U-2 were the same
size as the gliding balsa U-2 I expect the lead one would do as you
so delightfully describe, and glide "like a bowling ball".

[[email protected]]

Jim > wrote:

>On 28 Jul 2003 20:43:34 GMT, (B2431) wrote:
>
>>>>A U-2 constructed of lead would have the same glide ratio as one
>>>>constructed of balsa wood. It would glide faster, but just as far.
>>>>vince norris
>>>
>>>Say what?
>>>Dave
>>
>>Um, I think there's be a slight difference in wing loading which just might
>>have a minor affect on glide ratio. Translation: the lead U-2 would glide like
>>a bowling ball.
>>
>>Dan, U. S. Air Force, retired
>
>What a wonderful question. Glider pilots often add water ballast, 200
>- 300 lbs I think, to their gliders to increase airspeed at a GIVEN
>glide angle, thus improving the glider's penetration through the air
>at that glide angle. The extra weight does not alter the glide angle
>(except for very small improvements due to higher Reynolds numbers at
>the higher airspeed). The glider's descent rate is increased by the
>extra weight, but the airspeed is also equivalently increased so the
>glide angle remains (pretty nearly) constant, glide angle being a
>factor of only lift and drag, weight not even being in the
>calculation.
>
>As for a lead U-2 vs a balsa wood U-2, the lead U-2 would certainly
>glide as long as its wing loading was such that its wing could supply
>sufficient lift to sustain equilibrium in steady flight. The "catch"
>here is probably the inclination to picture the lead U-2 and the balsa
>U-2 as the same size. In such a case, if the lead U-2 were the same
>size as the gliding balsa U-2 I expect the lead one would do as you
>so delightfully describe, and glide "like a bowling ball".

But why would you go changing things?...if you're gonna do that
then you could have bigger wings, you could fit leading edge
slats, you could do lots to give one or the other the advantage.

I think that the only way to do these comparisons is to have big
ballast tanks fitted over the CG then play with weight.

Perhaps I'm getting old and slow but I'm having trouble seeing
how a glider (or an aircraft) can glide ...better?...
(farther/faster) when it's heavier.

I really don't follow your description about adding ballast
(above) at all...?

--

-Gord.

[RobbelothE]

Curious that no one has mentioned aspect ratio in the discussion. I guess I
should have included that in my original "lead-covered rock" post.



Ed
"Those who have long enjoyed such privileges as we enjoy forget in time that
men have died to win them."

Franklin D. Roosevelt, Address for Bill of Rights Day
15 Dec 1941

(Delete text after dot com for e-mail reply.)

[Tarver Engineering]

"Keith Willshaw" > wrote in message
...
>
> "Jack G" > wrote in message
> ...
> > Only in a vacuum would both "glide" at the same speed and go the same
> > distance - I think.
> > Jack
> >
> >
>
> In this case you are probably right but there is some truth in the
> assertion.

No, my idiot.

[Jim Knoyle]

(snip)

I realize this has nothing much to do with this discussion of glide ratio
but you've just dug up a memory/question.
A couple instances back around Iraq #I when I was out running in
the Palo Alto Baylands when I would pretty much stop and watch in
awe as a U-2R2 would take off from Ames Moffett about three
miles away. The aircraft would fly a perfect straight line in pretty
much an up-westerly direction until I would lose the speck in a
perfectly clear sky directly overhead. Yes, I did the 360 deg.
twist to verify the directly overhead part. Always wondered
where it may be heading.
JK (recalling the great old sights and sounds living near Moffett)

[Kirk Stant]

Jim > wrote in message >...
> On 28 Jul 2003 20:43:34 GMT, (B2431) wrote:
>
> >>>A U-2 constructed of lead would have the same glide ratio as one
> >>>constructed of balsa wood. It would glide faster, but just as far.
> >>>vince norris
> >>
> >>Say what?
> >>Dave


Within limits, weight has no effect on glide ratio (or Lift/Drag,
L/D). As has been mentioned, the speed that the plane achieves that
glide ratio goes up, by a function of the increase of the wing
loading. My glider (an LS6-b, a racing 15 meter glider) carries over
300 lbs of water for strong days - which increases my wingloading from
about 7.5 psf to over 10 psf. Wet, my average cross country speeds go
up about 10 mph (this is when lift is strong and consistent). My sink
rate goes up a bit, but in strong thermals (average acheived rate of
climb of 400fpm or more) the glide speed increase is worth it.

And of course, when the lift gets weak, we dump the water and creep in
- at up to 40/1, in my case!. Using a conservative 30/1 L/D, you can
go a LONG way from 17,999ft!

There is also a small theoretical increase in performance due to the
increases Reynolds number at the higher speed, but this is perhaps .5
to 1 L/D point.

Basic aerodynamics, guys!

Kirk
Phantoms Phorever, but real planes don't need no stinkin engines!

[[email protected]]

(Walt BJ) wrote:

>Glide distance - if you take the same airplane, it will glide farther
>if it's heavier.

I have a lot of trouble with that statement Walt...perhaps I'm
slow but I cannot see that at all.

>I mean normal load ranges from empty to MTOGW, not
>'balsa' and 'lead'. The reason is that there is more potential energy
>(energy of height) in the heavier-loaded one. Yes, the heavier bird
>does have to glide faster to maintain best L/D. This is depicted in
>the engines-out glide charts in the performance manuals of jet
>airliners. I gave my manuals away when I retired but trust me, it's
>there.
>Walt BJ

Yes Walt, I can see that the heavier a/c would have more energy
(potential energy?) but wouldn't it lose that advantage by the
fact that It's heavier and therefore require more energy to carry
that extra weight?...just sounds like 'getting something for
nothing' otherwise. IOW, if an a/c will 'glide farther' when it's
heavy then why wouldn't it 'fly further' when it's heavy under
power?. And it sure won't.

I'm not trying to be argumentative, I just can't grasp it...
--

-Gord.

[steve gallacci]

Thinking of the question from a different angle - the wing needs a range
of speeds to give good performance (lift versus drag) and the weight
dictates how much lift, and therefore speed, will be needed. An
extremely light load will need less speed to create enough lift, but
below a certain speed, the wing's drag vs lift will get in the way, and
though it is going very slowly, both forward and down, the glide ratio
may not be all that good. As weight increases, the speed necessary
increases as well, and there is a best combination of speed vs lift vs
drag for best glide ratio. Excessive weight will demand yet more speed,
but drag increases as well, so the glide ratio suffers. Our theoretical
balsa versus lead U2 might, ironically, have not dissimilar glide
ratios, while the real thing at an intermediate weight, have the better ratio.

[Jim]

On Tue, 29 Jul 2003 01:19:30 GMT, "Jack G" >
wrote:

>I am trying to make sure I understand this concept so please humor me.
>
>Clarification: Glide Ratio is the distance traveled forward for each
>equivalent distance traveled vertically. Is Glide Angle the same thing but
>measured in degrees?
>
>If two aerodynamically identical gliders (but one being heavier) are
>launched in a straight line from the same vertical distance with the same
>horizontal force, they will both arrive at the same horizontal distance from
>the launch point, but the heavier one will take less time to get there.
>
>This will be true only if the lift generated can sustain a glide ratio of >
>0:1
>
>
>This is where I get confused:
>
>Does the lift required to sustain a glide ratio > 0:1 increase as the weight
>of the glider increases?
>
>Your help IS appreciated!
>
>Jack
>

Glide angle, as I use the term, is the angle of the glide relative to
the horizon.

Yes, the lift force required to sustain an aircraft in un-accelerated
flight is proportional to the gross weight of the aircraft. For
instance, if 300 lbs of water ballast is added to a glider then the
lift required to maintain a given, un-accelerated glide ratio, or
glide angle, is increased as required to offset the additional 300
lbs.

Since the glider's wing size and shape are not altered simply by
the additional water ballast, and the wing now must produce additional
lift to maintain the additional 300 lbs, the glider must fly faster in
order to produce the additional lift force required.

In a way perhaps, this is kind of good news and bad news depending
on what the pilot wants. With the additional weight, the glider MUST
fly faster at a given glide ratio, on the other hand, the glider thus
CAN fly faster at a given glide ratio. Remember, the glide ratio
itself is not altered (significantly) by the added weight.

A glider pilot will want a glider that CAN / MUST fly faster at a
given glide ratio if he/she wants to cover distance quickly,
such as in a competition. However, the additional weight of the water
ballast will require stronger thermals for the glider to gain or
sustain altitude. If the thermals are weaker than the pilot had hoped
for he/she can dump the additional water ballast to lighten the wing
loading so as to make use of the weaker thermals -- but thus giving up
the ability to fly faster.

All this can confuse me too, and I often have to think it through
again.

One other note; with the added weight of the water ballast the glider
CAN / MUST fly faster at a given glide ratio, which is good for
covering distance quickly but the faster speed will put the glider on
the ground faster if no thermals or other lift sources are found.

Have I managed to make any sense?

[[email protected]]

Ron Parsons > wrote:

>
>Back in the last century when as students we used to have to do
>simulated flameout approaches to fields down near the Rio Grande with
>Cessna T-37's, it was quickly discovered that if you dived at a field
>that you were too close to, you would end up overshooting but if you
>pulled the nose up almost to a stall, you could mush down at a great
>angle.

But that doesn't make sense Ron...you certainly would end up at
the field with too much airspeed but why would you 'overshoot'
the field?...hell you could 'pointer straight down' and you
certainly wouldn't 'overshoot the field' (although you'd be going
like a scalded cat - and may need to 'overshoot' for that reason)
--

-Gord.

[Ron Parsons]

In article >,
"Gord Beaman" ) wrote:

>Ron Parsons > wrote:
>
>>
>>Back in the last century when as students we used to have to do
>>simulated flameout approaches to fields down near the Rio Grande with
>>Cessna T-37's, it was quickly discovered that if you dived at a field
>>that you were too close to, you would end up overshooting but if you
>>pulled the nose up almost to a stall, you could mush down at a great
>>angle.
>
>But that doesn't make sense Ron...you certainly would end up at
>the field with too much airspeed but why would you 'overshoot'
>the field?...hell you could 'pointer straight down' and you
>certainly wouldn't 'overshoot the field' (although you'd be going
>like a scalded cat - and may need to 'overshoot' for that reason)

Never been to the Rio Grande Valley I presume. All those nice flat
fields have palm trees as a fence row. Granted you could make a vertical
hole, but the point is to get over the near palms, get on the ground and
stop before you arrive at the far palms.

This was in the days when Primary was conducted by civilian instructors,
most of whom expected you to brush tall grass with your wheels on such
approaches and then go around.

My instructor at the time was a bit more than a civilian. He taught us
in the T-34 and T-37 and was still finishing up a few stragglers in the
T-28. He was also in the Texas ANG where he was an instructor in the
T-33, flew the F-86D and was qualifying in the F-102. He used to say,
"Just don't ask me any numbers. "The only time he ever touched the stick
with me was on the last day when he took the bird for a few minutes on
the way home. One of the smoothest I've ever ridden with.

--
Ron