Glide ratio with full brakes and side slip

Le mardi 3 mai 2016 06:30:09 UTC+2, George Haeh a écrit*:
Drag increases with the square of the
airspeed; so increasing your airspeed
from 55 to 75 increases drag by 86%.

With full brakes you can point reasonably
modern gliders at the threshold and come
down at a constant airspeed. Once you
level off the airspeed comes off rapidly
with full brake. Ground effect and weight
come into play, but even in a G103A it
doesn't take that much more runway than
a 2-22. Note that I stick to sideslipping in
the 2-22.

It can be hard on the guy in the back seat
hoping that the guy in the front seat will
round out before smacking the nose.

And if you round out too high and close
the brakes, you will be getting up close
and personal with the fence at the other
end.

As others said before - try that with a DuoDiscus, and tell us what the insurance said.

On Tuesday, May 3, 2016 at 12:30:09 AM UTC-4, George Haeh wrote:

With full brakes you can point reasonably
modern gliders at the threshold and come
down at a constant airspeed. Once you
level off the airspeed comes off rapidly
with full brake.

I've a friend who does this in a PW-6 from 1000 AGL on short final and have been in the back seat several times. I've done many steep finals at 70-80 knots due to turbulence, so I've given it some thought.

My understanding is that the flare expends the energy used to generate the lift that arrests the vertical speed, and that expenditure of energy reduces the horizontal speed in the flare. Do I have that right?

maanantai 2. toukokuuta 2016 15.49.11 UTC+3 Jim Kellett kirjoitti:

snip

Interesting. I've not flown the Duo very much, and never when I really needed a steep approach, so I can't contribute to any discussion of the peculiarities of that ship. On the other hand, I teach only in G-103s and K-21s, having given up teaching in Schweizer iron entirely about ten years ago. (For sure, a forward slip in a 2-33 is seriously effective at losing altitude, so no argument there!) And, yes, I wss surprised to learn some years back from a colleague who'd been flying in Europe about their practices of full spoiler/increased speed approaches - my first reaction was that it would get really busy in the cockpit at the roundout and touchdown to transition to a slow speed touchdown, but when I tried it, it turned out to be surprisingly easy and really effective.

Well, not all gliders are the same. I've heard the sentence "I teach this useless thing only because it is required in XXX" too many times. It is required because it is probably very important thing in *some gliders*, not all of them.

I've landed out old Duo couple of times and newer X model (with tiny flaps) too. Every single landing had to be done with full sideslip on final, and required field length was scary compared to light single seaters. I would not sign off anyone to fly Duo without excellent sideslipping technique. Good method is to tell student to fly the whole approach without airbrakes until at treetop height.

On Wednesday, May 4, 2016 at 8:54:50 AM UTC-4, krasw wrote:
maanantai 2. toukokuuta 2016 15.49.11 UTC+3 Jim Kellett kirjoitti:

snip

Interesting. I've not flown the Duo very much, and never when I really needed a steep approach, so I can't contribute to any discussion of the peculiarities of that ship. On the other hand, I teach only in G-103s and K-21s, having given up teaching in Schweizer iron entirely about ten years ago.. (For sure, a forward slip in a 2-33 is seriously effective at losing altitude, so no argument there!) And, yes, I wss surprised to learn some years back from a colleague who'd been flying in Europe about their practices of full spoiler/increased speed approaches - my first reaction was that it would get really busy in the cockpit at the roundout and touchdown to transition to a slow speed touchdown, but when I tried it, it turned out to be surprisingly easy and really effective.

Well, not all gliders are the same. I've heard the sentence "I teach this useless thing only because it is required in XXX" too many times. It is required because it is probably very important thing in *some gliders*, not all of them.

I've landed out old Duo couple of times and newer X model (with tiny flaps) too. Every single landing had to be done with full sideslip on final, and required field length was scary compared to light single seaters. I would not sign off anyone to fly Duo without excellent sideslipping technique. Good method is to tell student to fly the whole approach without airbrakes until at treetop height.

The method described to students above leaves the pilot with no options if sink or wind change occurs. It is outright dangerous and should not be taught.
It teaches a habitual low sight picture that is certainly not what students should be learning. They need to learn to make steep approaches with optimum energy management.
UH

At 11:30 30 April 2016, Jim Kellett wrote:

In a modern glider, the side slip is GREAT for crosswind landings, but
the
=
forward slip is darn near useless for losing altitude. I teach forward
sli=
ps to students only because it's in the PTS, but I teach full spoilers
and
=
increased speed to get a steep approach. That works like a charm,
produces=
a glide ratio WAY lower than 1:7, and is a lot easier to manage than it
so=
unds.

Wow! That is scary!!!

I agree with Jim. We call this descent profile a BDM (Barber Descent Method). Mr Barber imported this concept while flying Duo's in Switzerland. Works incredibly well. You can be 1000' on short final and still land on the numbers.
Forward slips in fiberglass ships are old school and rather underwhelming in a K, 103 or my 27.
I use the BDM in my ASW27, full flaps & spoilers and 80kts max, looks like a helicopter approach. No trouble recovering to standard glide path and speed. I estimate an L/D of 2 or 3:1, perhaps steeper in an ASK or 103.

XZ

On Friday, April 29, 2016 at 4:40:57 AM UTC-4, wrote:
I was wondering if anyone had an idea of what sort of glide ratio you get with full brakes and slide slip? An instructor used this to correct a very high approach but I was curious what the side slip adds to the descent rate.

Its a Forward Slip...Not a side slip...

Reminds me of a radio broadcast overheard, Pilot: "Tower Cessna November 123 with information alpha, inbound for landing" Tower: Cessna November 123 would that be a Cessna 150 or a Cessna Citation.


On Wednesday, June 8, 2016 at 11:06:06 AM UTC-7, 4881828 wrote:
On Friday, April 29, 2016 at 4:40:57 AM UTC-4, wrote:
I was wondering if anyone had an idea of what sort of glide ratio you get with full brakes and slide slip? An instructor used this to correct a very high approach but I was curious what the side slip adds to the descent rate.

Its a Forward Slip...Not a side slip...

Related, but sorta off topic.

I was flying a C-150 at a sorta busy regional airport with my CFI, I was number 7 in the pattern. Tower called me and asked if I could speed up because of a twin behind me, I answered, "cannot comply, full throttle as it is........ Permission to do a 360 to let the twin pass?" , reply was, "permission granted to do 360".

My instructor thought it was a good response by me to an odd situation.......

Originally Posted by 4881828

On Friday, April 29, 2016 at 4:40:57 AM UTC-4, wrote:
I was wondering if anyone had an idea of what sort of glide ratio you get with full brakes and slide slip? An instructor used this to correct a very high approach but I was curious what the side slip adds to the descent rate.

Its a Forward Slip...Not a side slip...

I've only ever done side slips. Maybe if I lived somewhere else in the world I may have been doing forward slips instead lol