Glide ratio with full brakes and side slip

[[email protected]]

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.

[[email protected]]

I think the average glider goes down to 1:5 when opening airbrakes.

[Per Carlin]

To be certified has the ratio with full airbrakes to be less than 1:7.

[Charlie M. (UH & 002 owner/pilot)]

I think some also depends on the glider, some don't come down much faster in a slip compared to others. Glass ship won't add much drag slipping compared to a 2-33 in a slip.

[Tango Whisky]

Le vendredi 29 avril 2016 14:47:09 UTC+2, Charlie M. (UH & 002 owner/pilot) a écrit*:
> I think some also depends on the glider, some don't come down much faster in a slip compared to others. Glass ship won't add much drag slipping compared to a 2-33 in a slip.

If you're slipping a ASK21 with full airbrakes, you are going down with an L/D of 3 or worse. In most glass two-seaters, slipping will increase the drag significantly.

[[email protected]]

My Pilatus B4 shows almost no effect for slipping, but comes down like a stuka with airbrakes.

[Bruce Hoult]

On Friday, April 29, 2016 at 11:20:42 PM UTC+12, Per Carlin wrote:
> To be certified has the ratio with full airbrakes to be less than 1:7.

At normal approach speed.

Many gliders will do 1:2 or even 1:1 at max airbrake speed (and some few 1:0). However it will then take 500 meters to slow down, so you're better off using a slip at reasonable speed unless the steep dive with brakes will bring you down to a normal approach angle well before the threshold.

When I was doing my cross-country rating in a Std Libelle it was at an away airstrip with a 10 feet high windbreak hedge at the start of the field. After a local soaring flight and standard landing the instructors said "Good. Now go and do another, but this time turn final at the same place but at 1000 ft instead of 300 ft and see if you can get it down". I threw in a full top rudder slip during the turn to final and held it in until about 100m before the fence. And landed shorter then the previous approach.

The Janus also slips scarily well, the Twin Astir not so much, and the DG1000 somewhere in between.

[Echo]

On Friday, April 29, 2016 at 10:26:11 AM UTC-5, Tango Whisky wrote:
> Le vendredi 29 avril 2016 14:47:09 UTC+2, Charlie M. (UH & 002 owner/pilot) a écrit*:
> > I think some also depends on the glider, some don't come down much faster in a slip compared to others. Glass ship won't add much drag slipping compared to a 2-33 in a slip.
>
> If you're slipping a ASK21 with full airbrakes, you are going down with an L/D of 3 or worse. In most glass two-seaters, slipping will increase the drag significantly.

Not sure about that. One demo I've done with students is to fly the final at 6-700' until the runway disappears under the nose. Full brakes and nose on the numbers. Gets some speed going but gets down by 1500.'

By comparison my ASW20 with the deep flaps comes down at 4:1 with the boards out and flaps at 60 degrees. According to the book anyway. I feel like that A model 20 can come down steeper than the 21...

Jordan Pollock

[N97MT]

> Many gliders will do 1:2 or even 1:1 at max airbrake speed (and some few 1:0). However it will then take 500 meters to slow down, so you're better off using a slip at reasonable speed unless the steep dive with brakes will bring you down to a normal approach angle well before the threshold.
>

1:0) <---- Emoticon of the student in the front seat the first time you demonstrate a slip at max airbrake speed to landing.

Learn to enjoy slips...it will save your bacon one day.

[Jim Kellett]

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.

<snip>

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 slips 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 sounds.

[[email protected]]

On Saturday, April 30, 2016 at 4:30:08 AM UTC-7, 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 slips 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 sounds.

That's interesting... My ASH-26E is limited to 76 knots with full flaps, so if I find myself a little high a slip brings it down like a falling rock!

-5Z

[[email protected]]

I fly a 2-22 and a 1-26, I dint need spoilers or a slip to come down like a tock.
Dan

[[email protected]]

Rock lol

[Jim Kellett]

On Saturday, April 30, 2016 at 1:27:33 PM UTC-4, wrote:

> That's interesting... My ASH-26E is limited to 76 knots with full flaps, so if I find myself a little high a slip brings it down like a falling rock!
>
> -5Z

Hmmm . . . my ASW-20C has a Vne or 65 kts with landing flaps, but I can get higher descent rates in the landing flap position by increasing airspeed than I can get with a slip! Yes, that IS interesting.

[[email protected]]

Jim are you hard slipping, meaning using all of your available rudder? Lots of guys don't realky rack it in there and consequently are not getting much drag effect from the fuselage. I had the oportunity to fly an early 20 and while not earth shattering, she would come down pretty good with a hard slip.
Dan

[Charlie M. (UH & 002 owner/pilot)]

Frankly, a "20" (especially an "A") with landing flaps & full airbrakes comes down fast.
If you "need" a slip, you are either waiting too long to pick a field or need to pick better fields.

The slip likely does not add much drag, more is likely lost from spanwise flow on the wing.

I have several hundred hours in 20 A & C models with too many safe off airport landings.

[[email protected]]

Or chasing a record and need to puther down in a pea patch over an 80 ft high hedge row

[[email protected]]

Been there done that

[[email protected]]

On Sunday, May 1, 2016 at 2:11:38 PM UTC-7, Charlie M. (UH & 002 owner/pilot) wrote:
> Frankly, a "20" (especially an "A") with landing flaps & full airbrakes comes down fast.
> If you "need" a slip, you are either waiting too long to pick a field or need to pick better fields.

Or in places like Colorado with big windshear and downbursts. I've flown a downwind with 50 knots on the tail and dead calm turning final. A few of these and you learn to fly high patterns and have the tools to get down if the wind quits on final. :-)

[krasw]

On Saturday, 30 April 2016 14:30:08 UTC+3, 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 slips 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 sounds.

This is the EXACT recipe how to destroy DuoDiscus while landing out. It is so exactly opposite to what you should do that it is almost scary. Probably works on 2-33 or whatever only-slightly-glider-shaped-object you teach on, though.

[Tango Whisky]

Le lundi 2 mai 2016 09:54:46 UTC+2, krasw a écrit*:
> On Saturday, 30 April 2016 14:30:08 UTC+3, 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 slips 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 sounds.
>
> This is the EXACT recipe how to destroy DuoDiscus while landing out. It is so exactly opposite to what you should do that it is almost scary. Probably works on 2-33 or whatever only-slightly-glider-shaped-object you teach on, though.

I totally agree. Side slip with a DuoDiscus works perfectly, and it does increase sink significantly.

You will always increase sink by increasing airspeed with full airbrakes - that will help you if you have a long apraoch without obstacles to bleed of the speed near the ground.

Ij you are landing into a 7-800 ft field over a line of trees, you can do that on a Duo by slipping, but increasing speed will result in a total loss claim.

[Z Goudie[_2_]]

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!!!

[Jim Kellett]

On Monday, May 2, 2016 at 3:54:46 AM UTC-4, krasw wrote:

> This is the EXACT recipe how to destroy DuoDiscus while landing out. It is so exactly opposite to what you should do that it is almost scary. Probably works on 2-33 or whatever only-slightly-glider-shaped-object you teach on, though.

<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.

[George Haeh]

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.

[Tango Whisky]

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.

[Jonathon May[_2_]]

At 09:31 03 May 2016, Tango Whisky wrote:
>Le mardi 3 mai 2016 06:30:09 UTC+2, George Haeh a =E9crit=A0:
>> Drag increases with the square of the=20
>> airspeed; so increasing your airspeed=20
>> from 55 to 75 increases drag by 86%.
>>=20
>> With full brakes you can point reasonably=20
>> modern gliders at the threshold and come=20
>> down at a constant airspeed. Once you=20
>> level off the airspeed comes off rapidly=20
>> with full brake. Ground effect and weight=20
>> come into play, but even in a G103A it=20
>> doesn't take that much more runway than=20
>> a 2-22. Note that I stick to sideslipping in=20
>> the 2-22.
>>=20
>> It can be hard on the guy in the back seat=20
>> hoping that the guy in the front seat will=20
>> round out before smacking the nose.=20
>>=20
>> And if you round out too high and close=20
>> the brakes, you will be getting up close=20
>> and personal with the fence at the other=20
>> end.
>
>As others said before - try that with a DuoDiscus, and tell us what the
>ins=
>urance said.
>


As a duo owner I can tell you it's not the LD that gets you it's the energy
that
you are carrying.
In the first generation if you lowered the nose enough to see where you
were
going the speed builds up,if you kept the speed under control you couldn't

see the field,however if you side slip you can see and control it all.
I have the later xlt and when the flaps deploy everything steadies up and
it is
great.If the engine is out the drag is off the scale.
But still the energy in the ground run is the big danger.

[krasw]

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.

[[email protected]]

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

[krasw]

keskiviikko 4. toukokuuta 2016 17.08.28 UTC+3 kirjoitti:
>
> 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

Glideslope can be managed by increasing sideslip angle, the altitude and approach slope are completely normal. And the options are plenty, they are sitting at the rear seat. I guess you are thinking about making approach very low for avoiding to use sideslip, which is not at all what I meant. The goal is to teach student to use sideslip completely naturally during approach, should they ever need it. If you have other ways to achieve that, that's just fine.

[son_of_flubber]

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?

[[email protected]]

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

I teach that dive brakes/spoilers control the rate of descent(at constant air speed) and control rate of deceleration in and after the round out. The change in drag resulting from the lift to arrest the rate of descent is pretty much meaningless compared to the power of the air brakes.
UH

[son_of_flubber]

On Wednesday, May 4, 2016 at 12:58:11 PM UTC-4, wrote:

> I teach that dive brakes/spoilers control the rate of descent(at constant air speed) and control rate of deceleration in and after the round out. The change in drag resulting from the lift to arrest the rate of descent is pretty much meaningless compared to the power of the air brakes.
> UH

Let's say the glide ratio of a steep descent is 1:7 and IAS is 70 knots when entering the flare. So the vertical component of the airspeed before flare is 10 knots. The horizontal component of the airspeed before the flare is 60 knots. (Are these assumptions correct?) After the flare the vertical component of the airspeed goes to +/- zero. What is the horizontal airspeed at the end of the flare? 60 knots?

[N97MT]

On Wednesday, May 4, 2016 at 1:01:08 PM UTC-5, son_of_flubber wrote:
> On Wednesday, May 4, 2016 at 12:58:11 PM UTC-4, wrote:
>
> > I teach that dive brakes/spoilers control the rate of descent(at constant air speed) and control rate of deceleration in and after the round out. The change in drag resulting from the lift to arrest the rate of descent is pretty much meaningless compared to the power of the air brakes.
> > UH
>
> Let's say the glide ratio of a steep descent is 1:7 and IAS is 70 knots when entering the flare. So the vertical component of the airspeed before flare is 10 knots. The horizontal component of the airspeed before the flare is 60 knots. (Are these assumptions correct?) After the flare the vertical component of the airspeed goes to +/- zero. What is the horizontal airspeed at the end of the flare? 60 knots?

Your airspeed vector during descent is the hypotenuse of an upside down right triangle. The long axis is the 7 horizontal component and the short axis is the 1 vertical component. The square of the hypotenuse is equal to the sum of the squares of the other two sides of that triangle.

My algebra tells me that at IAS 70 knots at the beginning of the flare, for a 7:1 descent rate, your vertical descent rate is around 9.9899 knots and your horizontal speed is around 69.2965 knots, not 60 knots.

If you are targeting 60 knots at the end of the flare, you need to burn off about 9 knots of excess horizontal velocity.

[George Haeh]

There are three states to consider
assuming constant wind:

Approach - Steady State if airspeed
constant and gravity vector at acute angle
to longitudinal axis and drag vector,

Round Out - my calculus is too many
decades stale, but note gravity vector
rotating to close to 90°.

Note the equations for transformation of
PE to KE do not take drag and lift into
account. Work is produced when force is
exerted over distance. Some of the papers
discussing windshear resort to differential
equations which would be needed to
analyze the round out.

Hold Off - Drag reducing airspeed, gravity
vector close to 90°.


At 15:39 04 May 2016, son_of_flubber
wrote:
>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?
>
>

[[email protected]]

Too much math for me, but after 6000 hours of glider and taildragger ive learned land with as low energy as is safe given the wind/gust factor. Do whatever it takes to get down with a non-flat or non-super steep approach angle. That may take 1/2 spoilers, full spoilers or full spoilers and slip, doesnt really matter as long as the energy is kept low.
Dan

[Charlie M. (UH & 002 owner/pilot)]

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..............

[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...

[Jonathan St. Cloud]

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...

[Charlie M. (UH & 002 owner/pilot)]

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.......

[Ventus_a]

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

[Bruce Hoult]

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.

[PGS]

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 Marotta]

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

[Shane Neitzey]

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

[PGS]

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,"

[[email protected]]

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.

[Martin Gregorie[_5_]]

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 |

[Casey[_2_]]

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.

[[email protected]]

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?

[Charlie M. (UH & 002 owner/pilot)]

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).

[[email protected]]

Charlie: could you explain what the "Snowbird" involves? (And say "hi" to my old friends at HHSC, if they're still there - it's been a long while!)

[Charlie M. (UH & 002 owner/pilot)]

Energy management mostly.
Each flight covers 4 items together:
-precision duration (usually multiples of 15 minutes timed to the second)
-touchdown in marked zones, touching before 1st zone is a big point hit, touching further is lessor hits
-stopping at a cone, scored to the inch
-cumulative altitude gain

So, duration 5 seconds off, touchdown in prime zone (no deduction), stopping within 5" of cone and no altitude gain would yield a score of 990 points.
You're allowed 2 flights Friday and 2 flights Saturday, a good year will require averaging high 900's!

HHSC's website should have more info on it, but that's the basics. It really measures energy management and pattern planning, good skills for off airport landings.