"Speed to fly"?

[Mxsmanic]

What does "speed to fly" mean when piloting gliders?

[Jim Logajan]

Mxsmanic > wrote:
> What does "speed to fly" mean when piloting gliders?

See page 7-34 of the FAA publication "Glider Flying Handbook" which is
online here:

http://www.faa.gov/library/manuals/aircraft/glider_handbook/media/faa-h-8083-13.pdf

[Stefan[_3_]]

Am 16.01.10 23:26, schrieb Jim Logajan:

> See page 7-34 of the FAA publication "Glider Flying Handbook"

Hum... They write "The object of speed-to-fly is to minimize the time
and/or altitude required to fly from the current position to the next
thermal." This is just plain wrong.

[george]

On Jan 17, 11:41*am, Stefan > wrote:
> Am 16.01.10 23:26, schrieb Jim Logajan:
>
> > See page 7-34 of the FAA publication "Glider Flying Handbook"
>
> Hum... They write "The object of speed-to-fly is to minimize the time
> and/or altitude required to fly from the current position to the next
> thermal." This is just plain wrong.

:-)
Whatever happened to best penetration speed ?

[Jim Logajan]

Stefan > wrote:
> Am 16.01.10 23:26, schrieb Jim Logajan:
>
>> See page 7-34 of the FAA publication "Glider Flying Handbook"
>
> Hum... They write "The object of speed-to-fly is to minimize the time
> and/or altitude required to fly from the current position to the next
> thermal." This is just plain wrong.

Wrong how? Note that they first write "Speed-to-fly refers to the optimum
airspeed for proceeding from one source of lift to another."

Others use the term similarly, e.g.:

"Speed-to-fly means selecting the optimum airspeed for cruising through a
given airmass, whether subsiding, still, or ascending. The goal is to
maximize distance flown per unit of altitude consumed. In a nutshell, you
can summarize the speed-to-fly concept as follows: fly slowly when in lift,
fly fast through sink, fly faster stil through very heavy sink."
- "The Art of Thermaling" by Bob Wander.

[Stefan[_3_]]

Am 17.01.10 01:16, schrieb Jim Logajan:
> Wrong how? Note that they first write "Speed-to-fly refers to the optimum
> airspeed for proceeding from one source of lift to another."

Yes, and that's wrong. Speed to fly is not the optimum speed to reach
the next thermal but rather to reach the target altitude in in that next
thermal. Otherwise, there would be absolutely no reason why you should
care about the strength of the next thermal.

You might argue that this is included in the word "proceeding", but I
doubt it, and even if it were, then that's certainly not clear enough
for somebody who has to ask.

> Others use the term similarly, e.g.:

You can cite as many authors as you like, if they copy their errors from
each other.

[Jim Logajan]

Stefan > wrote:
> Am 17.01.10 01:16, schrieb Jim Logajan:
>> Wrong how? Note that they first write "Speed-to-fly refers to the
>> optimum airspeed for proceeding from one source of lift to another."
>
> Yes, and that's wrong. Speed to fly is not the optimum speed to reach
> the next thermal but rather to reach the target altitude in in that
> next thermal. Otherwise, there would be absolutely no reason why you
> should care about the strength of the next thermal.

I'm afraid I still don't see anything in the sentence I quoted and what you
write above that are mutually exclusive in such a way as to indicate the
quoted sentence is "wrong." The brief discussion in its entirety in the FAA
handbook seems sufficient to answer the OP's question. However, a Google
search for the term by the OP, if he had bothered to even try it, would
have yielded plenty of useful hits giving more than adequate definitional
details - enough so that there would be no need to even post a query here.

> You might argue that this is included in the word "proceeding", but I
> doubt it, and even if it were, then that's certainly not clear enough
> for somebody who has to ask.

The FAA handbook's brief discussion seems adequate (IMVHO) for definitional
purposes.

As to authoritativeness, Bob Wander's books are well known on this side of
the Atlantic and often recommended for new glider pilots like myself.
Besides the rough definition I quoted from his "The Art of Thermaling"
book, he goes into more detail in his book "Glider Polars and Speed-to-
Fly."

(All his titles technically end with "... Made Easy!" You can go to his web
site, www.bobwander.com, and complain to him there about his verbiage. I
think he may also follow the soaring newsgroup too.)

>> Others use the term similarly, e.g.:
>
> You can cite as many authors as you like, if they copy their errors
> from each other.

What would you recommend as authoritative that defines the term to your
satisfaction?

[Stefan[_3_]]

Am 17.01.10 21:36, schrieb Jim Logajan:
> I'm afraid I still don't see anything in the sentence I quoted and what you
> write above that are mutually exclusive in such a way as to indicate the
> quoted sentence is "wrong."

Funny. If you don't understand the difference between the bottom and the
top of the next thermal, then I strongly suggest that you profit from
these cold days and read Reichmann's "cross country soaring" again.

> seems sufficient to answer the OP's question. However, a Google
> search for the term by the OP, if he had bothered to even try it,

Considering who was the OP, I strongly assume that he wasn't even
looking for an answer at all.

> The FAA handbook's brief discussion seems adequate (IMVHO) for definitional
> purposes.

How can a wrong definition be adequate?

> What would you recommend as authoritative that defines the term to your
> satisfaction?

The abovementioned Helmut Reichmann's "cross country soaring" would be a
perfect starter. (Since the book was written 1975 (translated to English
1978) you may consider it somewhat vintage, but on this side of the pond
it's still considered *the* standard, and as such it's regularily
reprinted.)

[Jim Logajan]

Stefan > wrote:
> Am 17.01.10 21:36, schrieb Jim Logajan:
>> What would you recommend as authoritative that defines the term to
>> your satisfaction?
>
> The abovementioned Helmut Reichmann's "cross country soaring" would be
> a perfect starter.

I may buy a copy. In the mean time, how does he define the term?

[Stefan[_3_]]

Am 18.01.10 22:00, schrieb Jim Logajan:

>> The abovementioned Helmut Reichmann's "cross country soaring" would be
>> a perfect starter.

> I may buy a copy.

I strongly suggest it.

> In the mean time, how does he define the term?

Ad hoc translation from the German book: "Speed to fly (in German
"Sollfahrt") is the speed that fits best your intention. Depending on
your situation it will be different." He then explains it over the next
30 pages.

[Gezellig]

On Sat, 16 Jan 2010 16:26:55 -0600, Jim Logajan wrote:

> Mxsmanic > wrote:
>> What does "speed to fly" mean when piloting gliders?
>
> See page 7-34 of the FAA publication "Glider Flying Handbook" which is
> online here:
>
> http://www.faa.gov/library/manuals/aircraft/glider_handbook/media/faa-h-8083-13.pdf

*ahem*

Point made.

[Jim Logajan]

Gezellig > wrote:
> On Sat, 16 Jan 2010 16:26:55 -0600, Jim Logajan wrote:
>
>> Mxsmanic > wrote:
>>> What does "speed to fly" mean when piloting gliders?
>>
>> See page 7-34 of the FAA publication "Glider Flying Handbook" which
>> is online here:
>>
>> http://www.faa.gov/library/manuals/aircraft/glider_handbook/media/faa-
>> h-8083-13.pdf
>
> *ahem*
>
> Point made.

Nolo contendere. I respond to aviation topics on r.a.p without (much)
respect for originator. Since it was on gliding - the only form of aviating
I've done so far - I happened to know a fairly authoritative online
reference and posted its link. I hoped more than the OP would get something
out of it, who I knew doesn't really fly.

Due to my reply I now know there are some differences of opinion on the
meaning of that phrase and got a recommendation for a good gliding book.
Worked out for me, anyway. :-)