drunkenbeagle
Gang Member
Slips are fine. But if the purpose is to ditch energy, it works better when you aren't in ground effect. And is safer.
Residential Street Glider 'Landing' Video
- Thread starter Jpax
- Start date
Slips are fine. But if the purpose is to ditch energy, it works better when you aren't in ground effect. And is safer.
killbilly
Vocals, Lyrics, Triangle, Washboard, Kittens
Waitasec.
I thought the purpose of a slip was to ditch ALTITUDE without INCREASING energy.
Granted, I have only flown powered aircraft....
Qutch
Question everything
Agreed, IN the ground-effect not necessary and not the safest perhaps under non-emergency conditions. But we practice them pretty low, sometimes only to burn off airspeed quickly just before touchdown. Good for short field landings under certain circumstances, like the OP video emergency. Just a thought.
Qutch
Question everything
You are correct. The FAA's Glider Flying Handbook describes the "primary" purpose for the foward slip the same way you do. Key word "primary." But not exclusive.
FAA Glider Flying Handbook
http://books.google.com/books?id=y1CCxCYbXEMC&pg=SA3-PA13&lpg=SA3-PA13&dq=glider forward slip&source=bl&ots=6Y42B0rjrK&sig=Za1ZlEpCju3pUQN7hix-smYmINg&hl=en&sa=X&ei=2y4EUOnUOsShrAHI1rGxDA&ved=0CFkQ6AEwBQ#v=onepage&q=glider forward slip&f=false
However, for the purpose of discussing the predicament that the OP/video found himself in, I was describing how I might have handled it in that type of emergency.......that is, with the same generous speed seen in the OP video (as insurance against unexpected ground turbulence, or other adverse conditions that make engineless go-arounds impossible), then a last minute forward slip all the way into the ground effect to drop the speed quuuuuickly. The way the OP handled it, he totaled the $8,500 sailplane, coming to rest on a pile of trash. He could have killed a resident floating down that road that far and at those speeds, and he nearly killed himself.
I wasn't necessarily recommending it as a daily approach/landing method for inexperienced pilots. However, it's a technique my retired Air Force flight instructor taught me when I was 15 for setting an aircraft/glider down on a dime, and I've practiced/used it ever since.
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Qutch
Question everything
Like the OP video, here's another interesting case of poor planning, and at a strip that's well known to be tough, St. Barts. In this case, the pilot had an opportunity to correct his mistake by going around, which he failed to do. No excuse.
However, if you presented me with a hypothetical situation like this video where I was asked to take over the controls, and a missed approach wasn't an option for some reason, I might try to employ a forward slip right off the deck in order to drop my speed. I'm not advocating it as a routine way to correct bad planning, or for inexperienced pilots. Just saying that, being comfortable and practiced with the technique, I might have used it. (This might be why no one will fly with me.
)
@Jpax , how crazy am I?
However, if you presented me with a hypothetical situation like this video where I was asked to take over the controls, and a missed approach wasn't an option for some reason, I might try to employ a forward slip right off the deck in order to drop my speed. I'm not advocating it as a routine way to correct bad planning, or for inexperienced pilots. Just saying that, being comfortable and practiced with the technique, I might have used it. (This might be why no one will fly with me.
)@Jpax , how crazy am I?
Inverted25
Well-Known Member
I wouldn't slip it either. Not that it's too dangerous but using full spoiler will do the job just fine. In a 1-26 at the right speed and full spoiler you will be coming down like a brick
Qutch
Question everything
That's part of the issue here. I'm not trying to "come down" and I'm not at the "right" speed. I'm already down to road level and my problem is bleeding off the excess speed that I chose to employ as an approach safety factor.
The OP was criticized for coming in too hot. Like the OP, I have a need for speed when flying gliders and bush planes in tough or uncertain conditions. Even flying powered under normal conditions, I come in with extra speed as conditioned from my glider/bush training. I assume that the engine will die on approach, just as I'm encountering wing-tip vortices and/or ground turbulence around hills or structures. Murphy's Law. So the plan is to use the extra speed to provide some margin for unexpected conditions, Then depending on the aircraft, use some combination of forward slip + spoiler/speed brakes + skid + boat anchor (if I have one to toss out) to drop the aircraft on a dime. I can't locate a video showing a glider doing this to the extreme, but I've seen it done in practice sessions. That's what I would have been trying to achieve on that residential street, if that street was really my only shot.
Let's ask rondebmar . He's flown a jet powered glider !
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TwoTwoLeft
o- - - - - - -l
Slips...
The only aircraft I've a done forward slip in that came remotely close to resembling a glider was a DA20 (Katana & Eclipse). It worked... Sort of. But not like what I'm used to. When I slip, I'm used to dropping out of the sky like a waxed manhole cover. These are dirty airplanes with glide ratios of 5:1 at their worst and 8:1 at their best. With so little fuselage, and those long wings, it seems that a forward slip wouldn't be very responsive in a glider, since sink rate is what you're looking for in a slip. Do spoilers get the job done better? Or can you use a combination of the two?
One thing I do find in the airplane world is that alot of pilots do not know how to effectively slip an airplane. About half think they do, and aren't afraid to try, but it's executed wrong (bad timing or sloppy control inputs). The other half never practiced it since their private checkride, and even then, were never taught right. They all just roughly apply the control deflections without knowing what they really want the airplane to do. I hate to say it, but that's mostly because their CFIs didn't know or weren't comfortable with it. In the beginning, I was never taught what to actually look for or why you slip. I just though it was fun to ask for short approaches and drop the 152 out of the sky from the numbers.
Here's a great example of using a slip to make the airplane do what you want! This is in a 7ECA (Citabria w/o flaps) IMO they were still a little fast & high over the tree tops, but well done none the less.
Some airplanes I'll slip into ground effect (Decathlon). Others I won't (most biplanes or swept wing airplanes) Wings (or spades) get too low to the ground and you want to be stable and lined up sooner. When slipping the DA20 I didn't have to worry since the mains kept it high enough off the ground, and the wing span wasn't that big compared to an actual glider.
In the video it looked to me like the pilot did the classic "haulin ass" emergency approach. A little extra speed is good, but not that much. Again, I don't fly gliders but that did look a bit overkill. When I teach off-field landings I'll have them pad an extra 5 on the approach speed. You can never tell if that's a 4" log or a 10" log from 1000agl, or you might need that energy to clear a ditch, powelines, Kim Kardashian, or other large undesirable objects.
The only aircraft I've a done forward slip in that came remotely close to resembling a glider was a DA20 (Katana & Eclipse). It worked... Sort of. But not like what I'm used to. When I slip, I'm used to dropping out of the sky like a waxed manhole cover. These are dirty airplanes with glide ratios of 5:1 at their worst and 8:1 at their best. With so little fuselage, and those long wings, it seems that a forward slip wouldn't be very responsive in a glider, since sink rate is what you're looking for in a slip. Do spoilers get the job done better? Or can you use a combination of the two?
One thing I do find in the airplane world is that alot of pilots do not know how to effectively slip an airplane. About half think they do, and aren't afraid to try, but it's executed wrong (bad timing or sloppy control inputs). The other half never practiced it since their private checkride, and even then, were never taught right. They all just roughly apply the control deflections without knowing what they really want the airplane to do. I hate to say it, but that's mostly because their CFIs didn't know or weren't comfortable with it. In the beginning, I was never taught what to actually look for or why you slip. I just though it was fun to ask for short approaches and drop the 152 out of the sky from the numbers.
Here's a great example of using a slip to make the airplane do what you want! This is in a 7ECA (Citabria w/o flaps) IMO they were still a little fast & high over the tree tops, but well done none the less.
Some airplanes I'll slip into ground effect (Decathlon). Others I won't (most biplanes or swept wing airplanes) Wings (or spades) get too low to the ground and you want to be stable and lined up sooner. When slipping the DA20 I didn't have to worry since the mains kept it high enough off the ground, and the wing span wasn't that big compared to an actual glider.
In the video it looked to me like the pilot did the classic "haulin ass" emergency approach. A little extra speed is good, but not that much. Again, I don't fly gliders but that did look a bit overkill. When I teach off-field landings I'll have them pad an extra 5 on the approach speed. You can never tell if that's a 4" log or a 10" log from 1000agl, or you might need that energy to clear a ditch, powelines, Kim Kardashian, or other large undesirable objects.
Qutch
Question everything
That was my instructor(s)' mindset, and now mine. An extra 5 in a powered aircraft sounds prudent. But in gliders there is no powered way out after we spot that log or ditch while encountering unexpected ground turbulence (which has a larger effect on featherlite gliders), so personally I'll cash my altitude in for speed, knowing that I can easily drop the speed once I've settled confidently over that road. Hence the emphasis placed on forward slip training by my particular sailplane instructors.
Thanks for the detailed analysis TwoTwoLeft.
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TwoTwoLeft
o- - - - - - -l
It's all about knowing what you're flying. If I were power off and 1/2 mile from the numbers at 500agl with no wind, in the Great Lakes my butt would pucker. If I were in the DA20, throw in 10 knots of headwind, still no sweat.
TwoTwoLeft
o- - - - - - -l
Pull the 'chute....?
In order to do this effectively you have to get on the backside of L/Dmax so you can start increasing AOA to slow down and stay down. This is what affects the speed you choose to make your approach. You can't have your cake & eat it too. If you have things like spoilers in your bag of tricks then you've got your answer. You need to somehow kill lift and increase overall drag. I don't see anything unsafe or wrong with slipping in ground effect as long as you know what to expect from it in the airframe you're flying. Although, I would think things like spoilers would make it much more predictable and prevent that "eternal float" that seems to come out of most slips... I say if you cant put it down where you want it out of a slip, then either get better at it or use something more effective.
It's really the same thing with TW pilots first learning to 3pt. You have ONE attitude to land at, you can't keep flaring like in a tricycle. Landing smoothly at that attitude is dependent on two things: Approach speed and the height where the 3pt attitude is set. Its all energy management.
drunkenbeagle
Gang Member
Potential energy = altitude
Kinetic energy = airspeed
From a physics point of view, both are interchangeable in a glider.
Losing altitude or losing airspeed serve the same purpose though in the end.
The energy state of the glider isn't ever going to increase. The only energy the glider has is due to gravity. The most effective way to lose that energy is to lose altitude, and that is best done by reducing lift (spoilers).
Adding drag (a slip) will make the glider descend faster as well, since more altitude will be consumed to maintain the a given airspeed. But it is nowhere near as effective as spoilers are.
TwoTwoLeft
o- - - - - - -l
killbilly
Same thing can be done in powered aircraft. I'll slip the Decathlon in ground effect to scrub off airspeed. With the semi symmetrical airfoil the approach tends to be rather shallow. When practicing power off 180s I just keep it a bit high and clean then drop it in over the power lines then slip it over the ground. It's good practice for off field landings and fun to do on acro rides!
Same thing can be done in powered aircraft. I'll slip the Decathlon in ground effect to scrub off airspeed. With the semi symmetrical airfoil the approach tends to be rather shallow. When practicing power off 180s I just keep it a bit high and clean then drop it in over the power lines then slip it over the ground. It's good practice for off field landings and fun to do on acro rides!
Qutch
Question everything
On another thread, rframe put up some pretty good documentation on the history of the trend away from spin training. I still urge pilots to get spin and acro training, but rframe's info made a good case that this training wasn't being done properly in too many cases, resulting in accidents. Thus the change in training philosophy, and the startled looks I get from today's CFI's when I suggest such "dangerous" training. I suppose that the use of the forward slip as a tool to bleed airspeed at the last minute may seem similarly odd, risky and unnecessary to many pilots, and depending on where and how the training is accomplished, they may have a point.
Some of my pre- Air Force training came from another group of resourceful and unconventional aviators. Bush Pilots. I love attending their STOL competitions. It's interesting listening to some of them talk about their reasoning process.
Heart Attack
drunkenbeagle
Gang Member
I slip the Pawnee all the way to the numbers, works great.
Aerodynamilly clean aircraft - not so much. Embarrassed myself trying to do the same thing in a cessna last month. Didn't work so well
With a glider - having a 40' wing that is only 3' above the ground WHEN LEVEL just doesn't allow much bank close to terra firma.
rvg203
Well-Known Member
I first saw this video at our Performance Soaring Seminar in March. It was included as part of a great presentation on landing out by U.S. Soaring Team member. I have been searching for this thing ever since, and found it on youtube a few days ago. I guess it has been only recently released to the "general public". A great training aid for sure!
In terms of slipping a glider in lieu of spoilers close to the ground, I find that it depends on what type of glider you are flying. This maneuver works fine in the old Schweizer metal (2-33, 2-32) as evidenced in the video of the white 2-32 slipping to land in the crosswind, but can be incredibly dangerous in glass ships.
We had an incident last year in which an extremely experienced CFI giving instruction came up short due to windshear performing a slip to land. There is practically no margin of error in this maneuver when performed in a high performance glass ship. A few knots too fast or a bit high for some safety, and you float all the way down the runway in ground effect, risking digging in a wingtip if the slip is continued to bleed off energy. An on glideslope, on speed slip to land in a high performance glass ship is even more hazardous, due there being no margin on the "back end" of the glideslope. If performed properly, the glider is at an extremely minimal glide angle at minimum approach airspeed (yellow triangle). There is no margin of safety for a sudden shift of wind direction or sink.
A 4 knot shear on extremely short final (less than 100 ft) brought the glider in question short of the runway and into the fence, on an otherwise perfectly executed slip to land approach. To truly land high performance glass without spoilers, you need to be at a glide angle and airspeed that offers no protection from a sudden shift of wind or unexpected sink. To date, it is the only NTSB report I have ever read with weather phenomenon being listed as the probable cause for the accident. Pilot error was not even listed as a contributing factor.
I have heard that the FAA is considering re- writing the PTS for Commercial/ CFIG in the "Slip to Land" department. The Glider PTS was written a long time ago, when all training gliders in operation could be safely slipped to a landing with adequate margin. High L/D, slippery glass training gliders didn't exist yet. Due to the date the PTS was written, it does not take into account that this maneuver can be incredibly unsafe in high L/D gliders, and is supposedly being rectified.
On another note, the failure mode that this maneuver is required to train for is extremely remote. I have never heard of, or know anyone that has heard of a spoiler deployment failure. That is not to say it never has or will happen, but the possibility is extremely remote. The most likely scenario I can see would be a wave flight with water present in the spoiler boxes. The water could freeze and prevent deployment of the spoilers.
In terms of slipping a glider in lieu of spoilers close to the ground, I find that it depends on what type of glider you are flying. This maneuver works fine in the old Schweizer metal (2-33, 2-32) as evidenced in the video of the white 2-32 slipping to land in the crosswind, but can be incredibly dangerous in glass ships.
We had an incident last year in which an extremely experienced CFI giving instruction came up short due to windshear performing a slip to land. There is practically no margin of error in this maneuver when performed in a high performance glass ship. A few knots too fast or a bit high for some safety, and you float all the way down the runway in ground effect, risking digging in a wingtip if the slip is continued to bleed off energy. An on glideslope, on speed slip to land in a high performance glass ship is even more hazardous, due there being no margin on the "back end" of the glideslope. If performed properly, the glider is at an extremely minimal glide angle at minimum approach airspeed (yellow triangle). There is no margin of safety for a sudden shift of wind direction or sink.
A 4 knot shear on extremely short final (less than 100 ft) brought the glider in question short of the runway and into the fence, on an otherwise perfectly executed slip to land approach. To truly land high performance glass without spoilers, you need to be at a glide angle and airspeed that offers no protection from a sudden shift of wind or unexpected sink. To date, it is the only NTSB report I have ever read with weather phenomenon being listed as the probable cause for the accident. Pilot error was not even listed as a contributing factor.
I have heard that the FAA is considering re- writing the PTS for Commercial/ CFIG in the "Slip to Land" department. The Glider PTS was written a long time ago, when all training gliders in operation could be safely slipped to a landing with adequate margin. High L/D, slippery glass training gliders didn't exist yet. Due to the date the PTS was written, it does not take into account that this maneuver can be incredibly unsafe in high L/D gliders, and is supposedly being rectified.
On another note, the failure mode that this maneuver is required to train for is extremely remote. I have never heard of, or know anyone that has heard of a spoiler deployment failure. That is not to say it never has or will happen, but the possibility is extremely remote. The most likely scenario I can see would be a wave flight with water present in the spoiler boxes. The water could freeze and prevent deployment of the spoilers.
tlewis95
I drive planes
All very good and true concering high performance gliders. The margin between 'too hot' and not making the runway is pretty small which is why I only really practice no-spoiler landings in really calm air in the higher performance gliders. But - the glider in the video isn't a high performance glider, it is a 1-26 (B model it looks like from other videos) that slips very well. The earlier models only have spoilers on the top side of the wing instead of the top and bottom so they aren't as effective as they could be but combined with a slip there is no reason you should not have enough drag to get down anywhere. I totally agree with adding extra speed for gusty or rough air on landing, but 5-8kts at most. To me it looks like the video 1-26 is doing about 15-20mph more then it had to be/should have been. The field off to the left of the road also looks quite nice (just from the video of course, who knows if there was a fence there) and I am wondering why the pilot didn't go for that besides the fact that he was way to fast to make it from his road approach, but if he were slowed down and trying for that field it should have been easily do-able.
Qutch
Question everything
I am however going to ask a stupid question,
@0:28 seconds in to this video, there is a patch of grass parralel to the road that goes between the two hills. Was it not suitable?
(OP Pilot Larry Hockensmith)
- You are correct about other suitable areas being available. At 0:28 seconds the field I selected was off the right wing, out of camera view. Another option would have been to setup a longer final approach to this field and land diagonally into it rather than making tight turns to the final for which I added airspeed.
LarryHockensmith - I was aiming for that field I had to pass over because of excess airspeed, street signs and cable vault in the brush. My guardian angel aimed me towards those soft, flexible trash cans.
LarryHockensmith - Actually, I had chosen that field much earlier in the flight. My approach to it was also designed to take me towards that notch in the ridg (directly ahead of plane) and possible escape to the valley. At "decision time" I saw the notch was not possible and executed my turn to a modified final. I kept too much airspeed, not wanting to stall during the needed turns. Perhaps forgetting the notch and setting up a longer final leg with speed controled would have worked better.
LarryHockensmith - I should have done a lot of things differently and better. That is exactly why I decided to share the video, so others can discuss and present their expertise in how the landing might have been flown. Please, you being a CFIG, post another reply with more detail on how a better approach would have been executed. I am not shy and you helping us all to learn will not offend me. Aviation is a very safe sport, and it takes learning to keep it that way.
LarryHockensmith
TowJoe
You really Schruted that one
Pilot's comments - worth reading
"Complacency has no place in soaring. I was trained better than to have lingered on the lee-side of a ridge over rough terrain. The dramatic outlanding was due to my actions exclusively.
While tight turns over roofs, brushing treetops and dodging street signs are not desired flight maneuvers, they do make for interesting viewing. An almost perfect (for a power pilot and plane but not a sailplane) landing until an unnoticed mailbox catches the right wing of the sailplane about 8 inches from the tip.
The original is 16 minutes of Full High Definition Video and shows every second of the events leading to this out-landing/ crash. It has been closely reviewed and much learning has taken place. My instructor, safety officer, FAA and NTSB were all outstanding professionals in helping grow skills from this experience.
More videos on this are coming. See if you can spot how the differences between a power pilot's training and a glider pilot's training could have contributed to this outcome."
--------------------
Critique posted from a glider tow pilot
"Larry, You've got to be flying a lot slower! You should be able to stop a 1-26 in about the length of a tow rope (shorter even). Touching down "two point" is the way to go. So many glider instructors never get their students to make a habit of low energy landings every time and this is a common result. I see the single wheel high speed landings all the time taught as a norm, it just doesn't make sense. Low speed and stick in your lap everytime is the way to go!"
(Qutch comment - I agree. That's the first thing I thought of. It really doesn't take that much runway to put down a glider. drunkenbeagle Inverted25 Nihon_Ni @rvg203, tlewis95 rvg203 @TowJoe ?)
.[/quote]
My experience is that my old boss, CFI-G, who flew basically every day, could put a Grob down in about 200 ft. The 1-26 I towed would do cross countries exclusively and never land back at an airport. The folks who flew often were really good with distances. Those who were the occasional flyer would sometimes take up 3/4 of the runway. However, these were always back at the origination airport. My point is that each situation is unique and from reading this pilot's posts it seems it was a very good learning experience that he was able to walk away from.
I have witnessed one glider clip a wing tip on very short final and survived. I know of another glider pilot/good friend whom I had towed a lot who did not survive.
I'll conclude with one thing that stuck with me from my instructing days that I read from AOPA--always stack the deck in your favor.
rvg203
Well-Known Member
It does look like he was flying a bit fast on approach. However, it would be interesting to know what the temperature and pressure on the ground that day was, as well as the elevation of the residential street. Density altitude could have increased his groundspeed a great deal. I just recently got back from Colorado, where I spent the week soaring. Temperatures were routinely above 100 degrees F with density altitudes greater than 10000 ft MSL. It took a lot more work thermalling due to the high density altitudes and increased groundspeeds. The same thing went for landing and takeoff rolls. They were much longer than normal.
While unknown, this could have been a huge factor in play during this landing. An illusion of being too fast could have been caused by an increased groundspeed due to DA, but the airspeed may have been near or on the mark. Although it did seem that he carried a bit too much airspeed in due to the prolonged float.
While unknown, this could have been a huge factor in play during this landing. An illusion of being too fast could have been caused by an increased groundspeed due to DA, but the airspeed may have been near or on the mark. Although it did seem that he carried a bit too much airspeed in due to the prolonged float.