Energy management

[Ian Cant]

The perennial contest finish argument is always entertaining.
May I, as an ignorant bystander, ask a related question
without being strafed too much ? If a finisher has
the energy for a fast low pass and then pullup to a
safe pattern, how much time along the course was spent
to acquire that energy to be dissipated after the task
is over ? Seems to me that there must be some points
loss involved, even if it's small. Except of course
for someone who is sure he has won by a large margin
and will get his 1000 - but even then, there is a points
gain for all the other competitors.

Ian

[Tuno]

Ian,

That's the question I posed in an earlier thread, and the answer (from
Andy) is that pilots consider it safer to bank a little extra altitude
in that last thermal before starting final glide, rather than risk
starting a final glide that's marginal, and then hitting sink, and
then finding nothing (or something very weak). This makes more sense
if you consider that thermals tend to be both stronger and farther
apart late in the day. In short it's just a risk management exercise.

I've read about some top pilots who believe in starting final glide
early (i.e., before having it), and "bumping" home, but this tactic
doesn't seem to have much of a following among the pilots I fly with.

Unlike how to cross a finish line as part of a landing pattern, the
topic of final glides has quite a bit of coverage in racing reference
materials...

~ted/2NO

[kirk.stant]

On Feb 13, 1:07 pm, "Tuno" > wrote:
> Ian,
>
> That's the question I posed in an earlier thread, and the answer (from
> Andy) is that pilots consider it safer to bank a little extra altitude
> in that last thermal before starting final glide, rather than risk
> starting a final glide that's marginal, and then hitting sink, and
> then finding nothing (or something very weak). This makes more sense
> if you consider that thermals tend to be both stronger and farther
> apart late in the day. In short it's just a risk management exercise.
>
> I've read about some top pilots who believe in starting final glide
> early (i.e., before having it), and "bumping" home, but this tactic
> doesn't seem to have much of a following among the pilots I fly with.
>
> Unlike how to cross a finish line as part of a landing pattern, the
> topic of final glides has quite a bit of coverage in racing reference
> materials...
>
> ~ted/2NO

To add a bit to Tuno's reply, it also depends a bit on the terrain
surrounding the finish. If there are miles of open fields surrounding
the finish, then one can (and really should) cut his final glide a bit
closer to the optimum. OTOH, at places like Turf, where the last 10
miles are totally unlandable tiger country, you better have enough
energy banked to make the finish no matter what!

Then, you need to get rid of that reserve of energy - speeding up gets
back a few of those seconds "wasted" climbing above the ideal final
glide height.

Which probably explains all those high speed finishes at Turf, eh,
Tuno? Works for me...

IMO, that's where one of the subtle traps of the "500ft at 1 mile"
finish creeps in. With all that pad, one is really tempted (and for
good racing reasons) to cut his glide real close. Then, when you get
to the line a bit too low to make it, you now have to decide if you
are going to try to pull up over it or take the penalty of a rolling
finish. Not an insurmountable decision, but it comes at the end of a
long day, you are tired, dehydrated, etc (does that sound familiar).

Bottom line - pilot in command is responsible for the safe conclusion
of the flight. Period. No excuses.

Kirk
66

[J. Nieuwenhuize]

All excessive speed that's left means spilled time... When you plan to
finish at 500' it's faster to leave early and make a (McReady) slow
glide to the finish line than to make a fast and low dash, which only
causes excessive drag. Of course it's very boring to ease back at 500'
instead of screaming alone with the crops hitting you're fuselage..

[kirk.stant]

On Feb 13, 5:54 pm, "J. Nieuwenhuize" >
wrote:
> All excessive speed that's left means spilled time... When you plan to
> finish at 500' it's faster to leave early and make a (McReady) slow
> glide to the finish line than to make a fast and low dash, which only
> causes excessive drag. Of course it's very boring to ease back at 500'
> instead of screaming alone with the crops hitting you're fuselage..

No disagreement, but if you need to carry some extra altitude for
safety (typically 500 to 1000 extra feet out here in the US SW), it is
faster to convert that altitude to speed when you realize that you
have the finish made safely. With a 500' at one mile finish, you want
to finish at 501 ft, and whatever speed that gives you. With a 50'
finish line, you would want to descend gradually and just hit 51 ft at
the line. While it sure is fun running in in ground effect (just
don't do it over people or things!) it isn't faster, at least with US
50 ft finish rules, since you would have to pull up to get across the
finish.

But as you say, diving down into ground effect specifically to extend
a glide will not help - better to just glide at L/D max to ground
effect, then float as long as possible. This is due to the energy
loss in the dive due to the pushover, pullout, and higher parasitic
drag at higher speed. Difference is small, but measurable.

Kirk
66

[HL Falbaum]

"J. Nieuwenhuize" > wrote in message
ups.com...
> All excessive speed that's left means spilled time... When you plan to
> finish at 500' it's faster to leave early and make a (McReady) slow
> glide to the finish line than to make a fast and low dash, which only
> causes excessive drag. Of course it's very boring to ease back at 500'
> instead of screaming alone with the crops hitting you're fuselage..
>

Traveling the final mile by trailer is pretty slow too. If you have ever
come up a little short on final glide due to increased sink, you might
change your mind.

Hartley Falbaum
DG800B "KF" USA

[HL Falbaum]

"Ian Cant" > wrote in message
...
> The perennial contest finish argument is always entertaining.
> May I, as an ignorant bystander, ask a related question
> without being strafed too much ? If a finisher has
> the energy for a fast low pass and then pullup to a
> safe pattern, how much time along the course was spent
> to acquire that energy to be dissipated after the task
> is over ? Seems to me that there must be some points
> loss involved, even if it's small. Except of course
> for someone who is sure he has won by a large margin
> and will get his 1000 - but even then, there is a points
> gain for all the other competitors.
>
> Ian
>
It appears that nobody has answered Ian's actual question (imagine that?)

The height gained in the pullup is equivalent to the total energy excess and
the "efficiency" of the glider in the conversion. Figure 90% for an open
classser, and about 85% for a current 15m ship (yeah, it's a W.A.G.) so if
the glider gets 600' on the pullup and has 85% efficiency, he had 705' of
total energy excess. If the last thermal was 4kt, then it took 1.76 min
extra to climb. If points are about 8/ min, then it cost about 14 points! If
running a street it gets a lot more complex as the streets are not uniform.

It is seldom so simple, as, unless the air is dying ahead, one must have the
power of prophecy to tell what is really going to happen.

Hartley Falbaum
DG800B "KF" USA

[g l i d e r s t u d]

The most effecient way to do it and loose the least amount of points.
Fly your normal inter-thermal speed on your final glide, get rid of
the saftey margin, fly it right down to the deck, put the gear down
and land. Straight in finish, Nimbus 3 1 mile out at 75knts 150ft agl
(maybe less). That is by far the MOST effecient way to do it, dont
give up any points.

However if you break the glider because you hit a little sink..well
then you just give up the contest. Personally I can make mistakes
myself without hurting anyone. Went to the NHRA winter nationals last
weekend, Top Fuel guys blow up engines on each run, some get more than
3 seconds before fire starts comming out of places its not supposed
to. If we had pit crews like that, then I might do final glides like
stated above. Since we dont, i'll put in a saftey margin, put in a
faster final glide speed and "burn off the altitude" at the end when I
know I got it made.

[J. Nieuwenhuize]

On 16 feb, 23:40, "HL Falbaum" > wrote:
> "Ian Cant" > wrote in message
>
> ...> The perennial contest finish argument is always entertaining.
> > May I, as an ignorant bystander, ask a related question
> > without being strafed too much ? If a finisher has
> > the energy for a fast low pass and then pullup to a
> > safe pattern, how much time along the course was spent
> > to acquire that energy to be dissipated after the task
> > is over ? Seems to me that there must be some points
> > loss involved, even if it's small. Except of course
> > for someone who is sure he has won by a large margin
> > and will get his 1000 - but even then, there is a points
> > gain for all the other competitors.
>
> > Ian
>
> It appears that nobody has answered Ian's actual question (imagine that?)
>
> The height gained in the pullup is equivalent to the total energy excess and
> the "efficiency" of the glider in the conversion. Figure 90% for an open
> classser, and about 85% for a current 15m ship (yeah, it's a W.A.G.) so if
> the glider gets 600' on the pullup and has 85% efficiency, he had 705' of
> total energy excess. If the last thermal was 4kt, then it took 1.76 min
> extra to climb. If points are about 8/ min, then it cost about 14 points! If
> running a street it gets a lot more complex as the streets are not uniform.
>
> It is seldom so simple, as, unless the air is dying ahead, one must have the
> power of prophecy to tell what is really going to happen.
>
> Hartley Falbaum
> DG800B "KF" USA

I did. Fastest final glide is always glide at McReady, and pull out
all the speed, so stalling, while crossing the finish line. If you
assume a minimum finish height this is way more efficient then
screaming along and probably not thát much unsafer.

[Ian Cant]

Thankyou, KF and all others. Am I correct to summarize
that there is a handful [or two, or maybe three handfuls]
of points to be lost by finishing low but with enough
surplus energy to pull up into a pattern rather than
finishing with minimum safe energy at any altitude;
that a safety margin should be carried right down to
the final few moments; that a straight-in and land
[either a rolling finish or after minimum-permitted
altitude finish] tactic on the remaining runway ahead
is the most 'efficient' provided it incurs no penalty;
and the balance between points grasped and safety and
showmanship is entirely at each pilot's discretion
?

Thanks again for the education,

Ian




At 22:42 16 February 2007, Hl Falbaum wrote:
>
>'Ian Cant' wrote in message
...
>> The perennial contest finish argument is always entertaining.
>> May I, as an ignorant bystander, ask a related question
>> without being strafed too much ? If a finisher has
>> the energy for a fast low pass and then pullup to
>>a
>> safe pattern, how much time along the course was spent
>> to acquire that energy to be dissipated after the
>>task
>> is over ? Seems to me that there must be some points
>> loss involved, even if it's small. Except of course
>> for someone who is sure he has won by a large margin
>> and will get his 1000 - but even then, there is a
>>points
>> gain for all the other competitors.
>>
>> Ian
>>
>It appears that nobody has answered Ian's actual question
>(imagine that?)
>
>The height gained in the pullup is equivalent to the
>total energy excess and
>the 'efficiency' of the glider in the conversion. Figure
>90% for an open
>classser, and about 85% for a current 15m ship (yeah,
>it's a W.A.G.) so if
>the glider gets 600' on the pullup and has 85% efficiency,
>he had 705' of
>total energy excess. If the last thermal was 4kt, then
>it took 1.76 min
>extra to climb. If points are about 8/ min, then it
>cost about 14 points! If
>running a street it gets a lot more complex as the
>streets are not uniform.
>
>It is seldom so simple, as, unless the air is dying
>ahead, one must have the
>power of prophecy to tell what is really going to happen.
>
>Hartley Falbaum
>DG800B 'KF' USA
>
>
>

[Bruce Greef]

Am I right that the reasoning behind the high speed low height dash is that it
takes one of the variables out of the risk equation?

You arrive at a point where you have the finish line made with some spare
energy, but not a lot.
If you fly the conservative approach at height you have an equal chance of
finding lift and/or sink over that last stretch.
Do this and there is uncertainty about the air you will fly through right up to
the finish line.

If you get right down into the stable layer right above the ground, the only
thing you have to worry about is running out of airspeed, height and ideas
simultaneously... But you did calculate this accurately with your flight
computer so not having to worry about vertical airmass movement is an advantage.
You can also fly above the rough air speed - you can be reasonably sure there
will be no significant vertical gusts under 50-100 feet AGL.

Finishing higher is safer for a number of reasons:
It presents a better view of the airfield, and other aircraft. (Less surprises,
better planning)
You can use the MK1 eyeball to confirm what your computer(s) are saying about
reaching the landing point.
If - for some reason you experience a malfunction, you have a little more time
to sort it out.
If - for some reason someone else does something unexpected, you have alternatives.
You have the luxury of slowing down and getting your mind out of race and into
landing gear - with time for a reasonable, predictable circuit so other people
know exactly what you are doing.

All the time based advantages in safety equate to points forfeited.

The personal level of risk accepted in the interests of winning is very
personal. Those making these low fast approaches presumably believe that it
improves their competitive position. But it helps to remember that you can't
race in a broken glider, or with a broken body.



Ian Cant wrote:
> Thankyou, KF and all others. Am I correct to summarize
> that there is a handful [or two, or maybe three handfuls]
> of points to be lost by finishing low but with enough
> surplus energy to pull up into a pattern rather than
> finishing with minimum safe energy at any altitude;
> that a safety margin should be carried right down to
> the final few moments; that a straight-in and land
> [either a rolling finish or after minimum-permitted
> altitude finish] tactic on the remaining runway ahead
> is the most 'efficient' provided it incurs no penalty;
> and the balance between points grasped and safety and
> showmanship is entirely at each pilot's discretion
> ?
>
> Thanks again for the education,
>
> Ian
>
>
>
>
> At 22:42 16 February 2007, Hl Falbaum wrote:
>
>>'Ian Cant' wrote in message
...
>>
>>>The perennial contest finish argument is always entertaining.
>>>May I, as an ignorant bystander, ask a related question
>>>without being strafed too much ? If a finisher has
>>>the energy for a fast low pass and then pullup to
>>>a
>>>safe pattern, how much time along the course was spent
>>>to acquire that energy to be dissipated after the
>>>task
>>>is over ? Seems to me that there must be some points
>>>loss involved, even if it's small. Except of course
>>>for someone who is sure he has won by a large margin
>>>and will get his 1000 - but even then, there is a
>>>points
>>>gain for all the other competitors.
>>>
>>>Ian
>>>
>>
>>It appears that nobody has answered Ian's actual question
>>(imagine that?)
>>
>>The height gained in the pullup is equivalent to the
>>total energy excess and
>>the 'efficiency' of the glider in the conversion. Figure
>>90% for an open
>>classser, and about 85% for a current 15m ship (yeah,
>>it's a W.A.G.) so if
>>the glider gets 600' on the pullup and has 85% efficiency,
>>he had 705' of
>>total energy excess. If the last thermal was 4kt, then
>>it took 1.76 min
>>extra to climb. If points are about 8/ min, then it
>>cost about 14 points! If
>>running a street it gets a lot more complex as the
>>streets are not uniform.
>>
>>It is seldom so simple, as, unless the air is dying
>>ahead, one must have the
>>power of prophecy to tell what is really going to happen.
>>
>>Hartley Falbaum
>>DG800B 'KF' USA
>>
>>
>>
>
>
>
>

[HL Falbaum]

"Bruce Greef" > wrote in message
...
> Am I right that the reasoning behind the high speed low height dash is
> that it takes one of the variables out of the risk equation?
>
> You arrive at a point where you have the finish line made with some spare
> energy, but not a lot.

In the USA the Sailplane Racing Association , and in Canada, the Candian
Advanced Soaring websites have excellent discussions on the subject
http://sailplane-racing.org/Articles/SRA/CompGuidev52%20Illustrated.pdf
http://www.sac.ca/cas/techniques/techniques.html

Books by Reichmann, Piggott, Welch & Irving explain the problem fully.

Modern flight computers can give you Total Energy corrected differential
final glide height. This means that at any time, the computer can tell you
how high above your "safety height" you would be when you reach the finish,
if you slowed to best glide speed-MacCready Zero, or in some computers, if
you slow to the set MacCready speed.

So you follow your MacCready directed speed until you see that you have the
field made--no doubt about it--. Either you see the airport at a comfortable
angle below your glidepath, or the computer says you are a good margin above
your safety height (500-1000 ft) that you have set-and you are just a few
miles (4-6) out. From that point you go to "visual" and burn as much height
as you think safe, while your computer tells you if you are gaining or
losing on the differential. If you set, say 500 in, and the differential
goes to zero, it means you can make it up to 500 if you slow down. Of
course--don't trust your life to this!

In general, a pull up from 120 kt to 60 kt recovers about only 450 ft. So
don't plan on a low 50 ft pass at anything less or you won't like what could
happen. If you are just crawling in, or walking at, say 80-90 kt, plan a
rolling finish, but announce it because you will be landing against the flow
of traffic! Better would be a high pattern---in the USA you lose points for
a rolling finish.

At any rate---These few points may make the difference between 1st and 3rd,
or between 21st and 22nd, but who cares? Nobody will remember if you won or
came in third that day, but they will remember a long time if you do
something stupid.

Hartley Falbaum
DG800B "KF" USA
850 points on a really good day!