The Yellow Triangle

On many German gliders on the ASI is a yellow triangle. This Yellow
Triangle on my ASw 20 and my LS3a is the factory recommended approach
airspeed. This speed is 49 knots. This has bothered me for a long time
now, I think the factory did alot of pilots a disservice by putting this,
to me anyway, very low number on there. On both the above gliders, the
max speed, normal landing flap flaps down, is 86 knots.

About 15 years ago my Gold Seal flight instructor Bob Faris, CX
,indicated to me in his LS3 he planned on a much higher speed in the
pattern, like 70 to as high as 80 knots depending on conditions. I
followed suit ever since.
I read in Soaring magazine frequently pilots stating that their in the
pattern around 50 knots, this makes the hair on the back of my head stand
on end! There is no margin for error at these low speeds. No reserve energy
at all.

Stalling and spinning in the pattern has been going on forever, generally
resulting in a awful crash.

I think we should all come up with a much higher speed in the pattern, and
trim for and hold that speed until about 20' off the ground, this could
eliminate alot of accidents IMHO.

I know all about the theory of adding half the windspeed and all of the
gust factor, never the less Airspeed is everything! As a group we have to
do better in this important phase of flight. What do you Glider Gods
think?

As an impeached ex-president (not PDJT) suggested - and at which other
respondents' replies hinted - it depends on what the meaning of "approach" is.
Do you mean "pattern speed" or "final approach speed"?

There's SO much in the nuances - this one and lots of others regarding "how
one flies a landing pattern".

Of the ~double-digits of late glider pilots I've known, I can recall only one
who died in the base-to-final turn...on an essentially windless, still,
day...at a camp, with lots of glider pilot witnesses (but not me). I've no
idea what her actual speed was at the time of departure from controlled
flight, but am satisfied it was almost surely "slower" than "faster"...and,
were it possible to settle the bet, would wager Real Money she was less than
perfectly coordinated during her last turn. "Slow speed" accident, or
"uncoordination-induced" accident?

Point being, there's at least one thing Joe Pilot - if interested in flying
again tomorrow - must *never* do, & that's depart from controlled flight in
the pattern. How s/he accomplishes that is the interesting bit...

As to "the yellow triangle", memory sez the only ships I semi-regularly flew
that had one were club-owned Grob variants. In benign approach conditions,
"triangle speed" seemed to me quite adequate (& comfortable) throughout the
pattern down to my "slowing down point" pre-flare. In "typical western-US
mid-boisterous day", still seriously percolating, atmospheric conditions...not
so much. Curiously, the two fastest approaches/finals I recollect were in a
G-103 (dual) and my Zuni, both "somewhere between 75-80 knots "somewhere along
upper-final-approach segment" as I recall, the Grob one due to downbursty
conditions, the other due to a howling (but remarkably steady &
lacking-in-turbulence) crosswind. I ultimately wheel-landed both, whereas in
calm conditions my default touchdown preference is the much-beloved 2-pointer.

Do what you have to do to touch down safely. Be able to do "it" consistently.
Stay away from "panacea cures" for the most part, if ever tempted to view them
as talismans in some way. Recognize any inherent paradoxes.

YMMV...

The yellow triangle marks is defined in CS 22.145 as the lowest approach speed (at maximum weight without water ballast) recommended by the manufacturer. So it should be treated as a minimum value without any margins.

Christoph

On Wednesday, February 17, 2021 at 7:32:39 AM UTC-8, Christoph Barniske wrote:
The yellow triangle marks is defined in CS 22.145 as the lowest approach speed (at maximum weight without water ballast) recommended by the manufacturer. So it should be treated as a minimum value without any margins.

Christoph

Spot on On Wednesday, February 17, 2021 at 3:50:01 PM UTC-8, 6PK wrote:
On Wednesday, February 17, 2021 at 7:32:39 AM UTC-8, Christoph Barniske wrote:
The yellow triangle marks is defined in CS 22.145 as the lowest approach speed (at maximum weight without water ballast) recommended by the manufacturer. So it should be treated as a minimum value without any margins.

Christoph

On Wednesday, February 17, 2021 at 10:32:39 AM UTC-5, Christoph Barniske wrote:
The yellow triangle marks is defined in CS 22.145 as the lowest approach speed (at maximum weight without water ballast) recommended by the manufacturer. So it should be treated as a minimum value without any margins.

Christoph

To be clear, my Discus 2b flight manual states the yellow triangle is the lowest approach speed at maximum mass without water ballast, with air brakes fully extended and landing gear down. For the D2B the triangle is marked at 54 kt IAS. That's over 20kts faster than the stall speed given in the flight manual for the same configuration.

In normal calm conditions where I fly near Ottawa, I try to be at, or just a few kts faster, than the bug speed on final approach but faster depending on wind and gust conditions.

Ian IN

Nicholas Kennedy wrote on 2/16/2021 4:56 PM:
On many German gliders on the ASI is a yellow triangle.
This Yelloe Triangle on my ASw 20 and my LS3a is the factory recommended approach airspeed. This speed is 49 knots.
This has bothered me for a long time now, I think the factory did alot of pilots a disservice by putting this, to me anyway, very low number on there.
On both the above gliders, the max speed, normal landing flap flaps down, is 86 knots.
About 15 years ago my Gold Seal flight instructor Bob Faris, CX,indicated to me in his LS3 he planned on a much higher speed in the pattern, like 70-75 knots depending on conditions. I followed suit ever since.

Since so many gliders have 49 knots for the Yellow Triangle, I think this might be a regulatory
requirement, not a choice by the glider manufacturer. Perhaps gliders are required to have an
approach speed no higher than 49 knots at a certain weight with the regulation required control
authority.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

On Thursday, February 18, 2021 at 8:11:35 AM UTC-5, Eric Greenwell wrote:
Nicholas Kennedy wrote on 2/16/2021 4:56 PM:
On many German gliders on the ASI is a yellow triangle.
This Yelloe Triangle on my ASw 20 and my LS3a is the factory recommended approach airspeed. This speed is 49 knots.
This has bothered me for a long time now, I think the factory did alot of pilots a disservice by putting this, to me anyway, very low number on there.
On both the above gliders, the max speed, normal landing flap flaps down, is 86 knots.
About 15 years ago my Gold Seal flight instructor Bob Faris, CX,indicated to me in his LS3 he planned on a much higher speed in the pattern, like 70-75 knots depending on conditions. I followed suit ever since.
Since so many gliders have 49 knots for the Yellow Triangle, I think this might be a regulatory
requirement, not a choice by the glider manufacturer. Perhaps gliders are required to have an
approach speed no higher than 49 knots at a certain weight with the regulation required control
authority.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

My D2B says 54 kts. The standard does not fix a given speed.
IN

My D2B says 54 kts. The standard does not fix a given speed.
IN

My SZD-55 says 56.7 kts/105 kph.
CS 22.1545 Air-speed indicator (See AMC 22.1545)
Each air-speed indicator must show the following markings:
.... some deleted ....
(e) a yellow marking (triangle) for the lowest approach speed (at maximum weight without water ballast) recommended by the manufacturer;
2D

On Thursday, 18 February 2021 at 13:11:35 UTC, Eric Greenwell wrote:
Nicholas Kennedy wrote on 2/16/2021 4:56 PM:
On many German gliders on the ASI is a yellow triangle.
This Yelloe Triangle on my ASw 20 and my LS3a is the factory recommended approach airspeed. This speed is 49 knots.
This has bothered me for a long time now, I think the factory did alot of pilots a disservice by putting this, to me anyway, very low number on there.
On both the above gliders, the max speed, normal landing flap flaps down, is 86 knots.
About 15 years ago my Gold Seal flight instructor Bob Faris, CX,indicated to me in his LS3 he planned on a much higher speed in the pattern, like 70-75 knots depending on conditions. I followed suit ever since.
Since so many gliders have 49 knots for the Yellow Triangle, I think this might be a regulatory
requirement, not a choice by the glider manufacturer. Perhaps gliders are required to have an
approach speed no higher than 49 knots at a certain weight with the regulation required control
authority.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

In the EASA CS22 specification for ASI markings it includes "a yellow marking (triangle) for the lowest approach speed (at maximum weight without water ballast) *recommended by the manufacturer*". (My stars). As far as I can see there is neither a set value nor a formula for deriving it from e.g. stall speeds

On Thursday, 18 February 2021 at 14:48:55 UTC, wrote:
On Thursday, 18 February 2021 at 13:11:35 UTC, Eric Greenwell wrote:
Nicholas Kennedy wrote on 2/16/2021 4:56 PM:
On many German gliders on the ASI is a yellow triangle.
This Yelloe Triangle on my ASw 20 and my LS3a is the factory recommended approach airspeed. This speed is 49 knots.
This has bothered me for a long time now, I think the factory did alot of pilots a disservice by putting this, to me anyway, very low number on there.
On both the above gliders, the max speed, normal landing flap flaps down, is 86 knots.
About 15 years ago my Gold Seal flight instructor Bob Faris, CX,indicated to me in his LS3 he planned on a much higher speed in the pattern, like 70-75 knots depending on conditions. I followed suit ever since.
Since so many gliders have 49 knots for the Yellow Triangle, I think this might be a regulatory
requirement, not a choice by the glider manufacturer. Perhaps gliders are required to have an
approach speed no higher than 49 knots at a certain weight with the regulation required control
authority.
--
Eric Greenwell - Washington State, USA
https://sites.google.com/site/motorg...ad-the-guide-1
In the EASA CS22 specification for ASI markings it includes "a yellow marking (triangle) for the lowest approach speed (at maximum weight without water ballast) *recommended by the manufacturer*". (My stars). As far as I can see there is neither a set value nor a formula for deriving it from e.g. stall speeds

There's probably some approximation or rounding

49 and 54 knots might sound like precision to us, but these are 90 and 100 km/h. 86 kts is 160 km/h