Glide ratio with full brakes and side slip

On Wednesday, June 8, 2016 at 9:06:06 PM UTC+3, 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...

A distinction without a difference. The aircraft has no idea whether your fuselage happens to be aligned with a runway or not.

On Thursday, June 9, 2016 at 9:06:58 AM UTC-4, Bruce Hoult wrote:
On Wednesday, June 8, 2016 at 9:06:06 PM UTC+3, 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...

A distinction without a difference. The aircraft has no idea whether your fuselage happens to be aligned with a runway or not.

Just to be clear, what Bruce is correctly stating is that there is no difference between a "side slip" and a "forward slip" with regards to aerodynamics. The difference is relative to ground track when a cross wind is present.

Why not just call them "slips" and eliminate the confusion? ;-)


On 6/9/2016 7:31 AM, pgs wrote:
On Thursday, June 9, 2016 at 9:06:58 AM UTC-4, Bruce Hoult wrote:
On Wednesday, June 8, 2016 at 9:06:06 PM UTC+3, 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...
A distinction without a difference. The aircraft has no idea whether your fuselage happens to be aligned with a runway or not.
Just to be clear, what Bruce is correctly stating is that there is no difference between a "side slip" and a "forward slip" with regards to aerodynamics. The difference is relative to ground track when a cross wind is present.

--
Dan, 5J

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 Thursday, June 9, 2016 at 11:18:12 AM UTC-4, Dan Marotta wrote:
Why not just call them "slips" and eliminate the confusion? ;-)


On 6/9/2016 7:31 AM, pgs wrote:
On Thursday, June 9, 2016 at 9:06:58 AM UTC-4, Bruce Hoult wrote:
On Wednesday, June 8, 2016 at 9:06:06 PM UTC+3, 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...
A distinction without a difference. The aircraft has no idea whether your fuselage happens to be aligned with a runway or not.
Just to be clear, what Bruce is correctly stating is that there is no difference between a "side slip" and a "forward slip" with regards to aerodynamics. The difference is relative to ground track when a cross wind is present.

--
Dan, 5J

To logical. Besides the FAA wants pilot applicants to be tested on these terms
"Exhibits knowledge of the elements related to forward, side,
and turning slips to landing,"

On Wednesday, May 4, 2016 at 11:39:52 AM UTC-4, son_of_flubber wrote:
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?

Flubber: the roundout is not much different from being in a turn at altitude: the lift is (more or less) perpendicular to the direction of travel, thus no "work" (force times distance along the direction of force) is done, thus no energy is burnt up. You need the drag to do that for you.

Moreover, when you round out close to the ground you encounter "ground effect", meaning reduced induced drag, lengthening the runway length needed to burn off the excess airspeed. Thus, if you do descend on final at a higher than normal airspeed, and if the runway is not very long, you may want to reduce the airspeed gradually, starting somewhat above "flare" level. With full spoilers adding a lot of drag, the speed should bleed off pretty quickly.

I used to fly a 1966 Cessna 172 with the 40-degrees "barndoor" flaps and with STOL mods (droop tips and leading edge cuff increasing camber). It could descend very steeply with full flaps, but once in ground effect it still floated quite a ways. I learned to make sure to keep the airspeed low (about 50 mph in that plane) if I wanted to stop on a short runway. Same in the HP14 I used to fly, with plenty of flaps it could come down VERY steep at moderate airspeeds.

That said, flaps and spoilers differ, flaps add lift (and drag), spoilers subtract lift (and add drag). What happens to the effect of the spoilers in ground effect? In my current glider -- the AC4a prototype with above-and-below way-more-then-necessary spoilers -- the spoilers seem to have a significant effect after flare and well into the rollout. Induced drag may be reduced in ground effect, but there's still some, plus the spoilers probably add parasite drag.

On Fri, 10 Jun 2016 08:36:40 -0700, moshe.braner wrote:


In my current glider -- the AC4a
prototype with above-and-below way-more-then-necessary spoilers -- the
spoilers seem to have a significant effect after flare and well into the
rollout. Induced drag may be reduced in ground effect, but there's
still some, plus the spoilers probably add parasite drag.

That matches my experience with my Std Libelle. When I first got it, on
one flight I underestimated its (minimal) airbrake power and by the time
I'd completed a slightly too fast flare, found that I was going to land
long enough to touch down just before a hard track that crosses our main
run. Not a good idea as the track is slightly proud of the grass surface.
Closing the brakes easily floated me over the track and re-opening them
made the glider settle once past it. The effect of closing and then re-
opening the brakes was quite noticeable, even when floating in ground
effect.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Wednesday, May 4, 2016 at 7:15:48 PM UTC-4, Charlie M. (UH & 002 owner/pilot) wrote:
This I will agree with.

I consider needing, "full dive brakes and a full slip" to get down means:
- I waited too long to pick a good field
- I did NOT manage energy correctly during the pattern (regardless of pattern length).

Sorta edit, in the past, I was requested by CFIG's that were better than I to demonstrate a "max, hang it all out" decent.
Yes, we should ALL push the envelope at the home field now and then to prepare for when when poor judgement/planning requires superior skills in the real world.
What's easy for me may be beyond what you can do..............


I'm a low time pilot, but seems to me that landing out and for some reason with a tail wind would be the number one situation of using full spoiler and slip. Pushing the envelope or practicing various landing skills at the home field seems to be advantages in ones preparation for non ideal landing fields or approaches,but wonder how many people practice.

On Friday, June 10, 2016 at 2:30:16 PM UTC-4, Casey wrote:
On Wednesday, May 4, 2016 at 7:15:48 PM UTC-4, Charlie M. (UH & 002 owner/pilot) wrote:
This I will agree with.

I consider needing, "full dive brakes and a full slip" to get down means:
- I waited too long to pick a good field
- I did NOT manage energy correctly during the pattern (regardless of pattern length).

Sorta edit, in the past, I was requested by CFIG's that were better than I to demonstrate a "max, hang it all out" decent.
Yes, we should ALL push the envelope at the home field now and then to prepare for when when poor judgement/planning requires superior skills in the real world.
What's easy for me may be beyond what you can do..............


I'm a low time pilot, but seems to me that landing out and for some reason with a tail wind would be the number one situation of using full spoiler and slip. Pushing the envelope or practicing various landing skills at the home field seems to be advantages in ones preparation for non ideal landing fields or approaches,but wonder how many people practice.

It is a challenge to practice non-home-field situations at the home field, but CFIGs should think of ways to do that. Of course can practice steeper than normal approaches. Can also practice landing on a different part of the home field than normal, e.g., further down the runway (within reason). Can land downwind on purpose (within reason). Beyond that? Fortunately the weather varies (around here anyway, New England is famous for that) enough to produce a lot of different flavors of pattern and landing.

Do any of you practice landings at other nearby airfields, complete with an aero-retrieve?

Great idea, done by sites in the NE US, look up the "Snowbird" out of HHSC every Thanksgiving weekend.

While it's a "last get together" for some of us, it's also a, "energy management endeavor" that translates to an off airport landing.
Consistency matters, not breaking the ship is best.

The rules of the "contest" tend to promote energy management. Being good at this helps prevent broken ships, thus, broken pilots.
Take this from one that has done well at the Snowbird, and has thus far not broken a ship (or myself).