SFO Crash Myths

[Artimi]

Is this another case of words changing meaning as they cross the Atlantic?  

[caesar novus]

It IS claimed in http://www.pprune.org/tech-log/464013-forward-side-slip.html that forward as applied to slip is mostly American, or limited to one sector of UK pilot types or other Europeans. This is appalling because the forward slip is a stunningly unique and useful technique. That's why it was such a miracle that a Canadian airline pilot used it right. And understandable why the French pilot I mentioned failed to take advantage.

The concept is super simple. Sideslips are your plane sliding to the side relative to the air. You partially check the slide by opposing it with your rudder, modulated to stay on track with a runway when the air you are in makes a crosswind.

The totally revolutionary concept, which surely needs a precise name... is when you mash that rudder hard to essentially check all slippage to the side... It's the ANTIsideSLIP or the forward slip because it only affects your forward glide slope. You can go steeper down and land without over speeding... Much safer without power because you can arrive high so as to prevent undershoot a la Asiana, then create a bunch of straight drag to avoid overshoot.

Just because the controlling is similar, and maybe you combine it with crosswind handling makes people casually think they are no different, or defined by your intention. But an absolutely straight relative to air

(rather the ground) forward slip is a lifesaver that needs a name for the different concept, because it isn't a logical extension of what calls for a sideslip.

Edited August 24, 2013 by caesar novus

[caldrail]

You keep trying to invent "forward slips". Bottom line - slips are lateral movements of an aeroplane in flight, also called skids when slipping outward in a turn. Whether caused by imbalance of lift and gravity, poor flying, or by intentional control input, the effect is the same. Crabbing or slipping is irrespective of the wind - it's the direction of travel that's important.

 

A conventional aeroplane will try to weathercock out of a slip because the rear fuselage area is greater than the forward, although some aeroplanes (The Handley page Hampden was one) do not easily recover from slips. Swept wing designs are not well suited to slipping for the reasons I've already given.

 

You will not find anyrthing called 'forward slip' in a british flight training manual.

[caesar novus]

I can agree with most of your previous post, except for the need of the world to know and love forward slips. It would do better with a new name, but an accurate one would sound nerdy... it is sort of a backwards slip, or more exactly a less-forward slip... how about parachutal mode!

 

Supposedly the ancient Greeks had 10+ words for love, which modern scholars reduced to 6 actual seperate concepts. But let's be sure the British aviation scholars haven't reduced their terminology down to a dangerous 5, such as would share the same term for sibling love as jealous, possessive love!

 

We could almost dispose of the whole nerdy world of slips other than forward ones. I hate the monitoring of slip vs skid during flying... let's say all new planes must have a switch to handle this by computer. I also would like to ignore the nerdy crosswind landing tricks... yeah, a crab is nothing special; it's just the normal way you always fly up high or anywhere pointing a bit into the wind to avoid missing your destination. Intentional sideslip for crosswind: let's say new planes can't be certified if they actually need them. You just fly down normally (crabbed), then kick the rudder pedals to halfway straighten on landing.

 

Forward slips: I have a ww2 british Mosquito manual and it says if you have to land without flaps you will descend with very flat angle. I believe much faster as well. This is a recipe for disaster because there will be so little room for error in under or overshooting the runway, especially without power. A (less) forward slip is the supreme answer. It's one of the first things a sailplane student learns. I can't vouch whether all US power pilots learn it before solo, because I went thru that at age 15 where my memory cells hadn't gelled yet.

 

Maybe forward slips are known and used in UK and elsewhere under the sideslip name, but I doubt it. If they merrily can come in crooked in an emergency, bless them, but I hope they max out that rudder (against weathercock) to a forward slip because anything more timid like a conventional sideslip will speed them up and be inefficient. There are differences with various dihedral, swept wing, etc but that can usually be worked around. The slip side swept wing will resist with increased lift, but in an emergency you can force it. Note dc10's and the air canada (767, 777?) do it.

 

Let's call it parachutal mode rather than forward slip. Just to be complete, someone might figure a comparable emergency maneuver involving a skid (to outside of turn)... sort of an anti-parachutal mode. You might approach runways long and high in a fast skidding turn, then (if needed) shorten/modulate the overshoot by snuffing the skid. Rudder would be used in opposite way as forward slip. I'm very unsure this would work, but I actually like curved approaches rather than rectilinear, invented I believe by UK carrier radial pilots who had poor forward visibility. I read that modern US pilots with poor forward visability (in a non-crosswind) may use the forward slip instead, to approach straight but point crooked!

Edited August 25, 2013 by caesar novus

[caldrail]

Flapless landings are always performed at a slightly higher speed to compensate for the lack of extra lift/drag and by necessity require a longer landing run. That's a standard part of ab-initio flight training.

 

 

Maybe forward slips are known and used in UK and elsewhere under the sideslip name, but I doubt it.

maybe "forward slip" is the incorrect term? I certainly believe that to be the case and so should you. A sideslip is a sideslip. Period.Since an aeroplane is moving relative to the medium of air, wind makes no difference unless it relates to movement compared to the ground. Further, using full rudder on a slip is potentially hazardous because it leaves you no further control input in the event of air fluctuations.

 

Other than that this "forward slip" business is nonsense invented by people who don't know anything about flying and want to sound clever.

[caesar novus]

The mosquito manual gave the exact speeds to use landing flapless, and although it is screamingly obvious that it ought to be faster... I didn't bother comparing the actual numbers. Thus I didn't use false certainty in spite of 99.99% chance. It is a case of me using precise language, and my life experience of knowing there are exceptions. The point the reader should draw is... Holy moley, how many mosquito planes and crew suffered damage due to not knowing parachutal mode. How many airliners too.

 

You seem to be reading forward SIDEslip vs forward slip. The former would be ridiculous, whereas a slip could logically be in any direction 360 degrees. It can't be confused with a skid because that has an upward component vs slips have downward. It is revealing that this proven miraculous procedure is so unknown, unused, and that you attack the message instead of appreciate its usefulness.

Edited August 27, 2013 by caesar novus

[caldrail]

When landing an aerplane you need to fly at the lowest speed possible commensurate with safety. The faster you approach the more likely you will 'float' on landing and risk an overrun or worse. Aircraft are suprising cpable to staying airborne when in ground effect. Parachutal mode? Not the slightest idea what that is although it does sund like another of your blind alleys. Actually it was ground loops that were the greatest bugbear in operating Mosquito's. After a series of accidents a very irate squadron leader addressed his men and told them in no uncertain terms that the Mosquito does not veer - "It's you stupid b******s that make the aeroplane swing!". Funnily enough the accident rate improved no end.

 

 

You seem to be reading forward SIDEslip vs forward slip. The former
would be ridiculous, whereas a slip could logically be in any direction
360 degrees. It can't be confused with a skid because that has an upward
component vs slips have downward. It is revealing that this proven
miraculous procedure is so unknown, unused, and that you attack the
message instead of appreciate its usefulness.

Go and learn some principles of flight. You clearly don't understand it - that paragraph contains some of the worst misconceptions about flying I've ever seen.

[caesar novus]

When landing an aerplane you need to fly at the lowest speed possible commensurate with safety. The faster you approach the more likely you will 'float' on landing and risk an overrun or worse. Aircraft are suprising cpable to staying airborne when in ground effect.

.

Pilots unfamiliar with forward slip may HAVE to come in dangerously fast or high. Like the Mosquito instructions for flapless landings. Or like the French airline pilot gliding back to his island of departure... he was at least wise to not risk arriving short (like Asiana at sfo) but came down with enough speed/height to overpower any little downdraft or miscalculation. The priority was to make the runway, and then somehow deal with the screeching overspeed.

 

Or for more informed pilots in the same situation, the forward slip can be used from a fast/high approach to safely soak up energy, then if you hit a downdraft or see need to avoid undershoot, then you pop out of forward slip early and have energy to extend glide as needed.

.

Parachutal mode? Not the slightest idea what that is although it does sund like another of your blind alleys. Actually it was ground loops that were the greatest bugbear in operating Mosquito's. After a series of accidents a very irate

.

Just giving you a functional term since you criticize the term forward slip. You are stuck on it implying "sideness". As I have repeatedly stated, and included videos and definition references... it is a dead ahead straight maneuver. Very much like the snowplow when skiing... one goes right (stick) and is exactly opposed by the other going left (rudder). Soaks up energy and allows more pinpoint landings when flaps/power not available.

 

It needs to be more widely known and practiced, not just an obscure one time thing to pass a test. I was amazed the Canadian airline pilot used it, until they explained he was also a sailplane pilot. Power pilots are pretty sloppy due to thinking the throttle will always respond to correct their mistakes. Sailplaners know to come in high/fast to guarantee no undershoot. Then they can use flaps, spoilers, or if they don't work "forward slip" to avoid overshoot/overspeed.

[caldrail]

Don't be ridoculous. According to your recent definition of "forward slip", it's just crabbing. That's a basic terchnique taught to every pilot during his initial training. Nothing obscure about it at all, although I should point out that the 'wing down' method is just as effective and in many cases better idea, since crabbing has the unfortunate aspect of sidweways travel along the ground which has to reduced befiore touchdown to avoid landing accidents, which will - as I soon found myself in real life - re-introduces the very same drift you're trying to avoid, the caveat with the 'wing-down' method being that wing tip strikes must be avoided and that the initial stress of touchdown is on one undercarriage member only, and then at an angle.

 

Anyone who comes in at dangerously hgih or fast is flying dangerously (and badly) thus has no just cause for doing so. Such an approach is indicative of poor planning on the approach, poor decision making, and poor flying.

 

Do get some education on principles of flight. Do it properly, not this internet rubbish.

Edited August 29, 2013 by caldrail

[caesar novus]

First of all, my point is only about airline and power pilots putting themselves at needless risk by the over trust of engines or flaps being available to correct during the last seconds of landing. Sailplane pilots and even second-day US student power pilots learn ways to harness the energy you already have in the form of altitude and speed, and how to modulate it by forward slip, etc. So you aren't in the position of needing to add extra (unreliable) energy, but more or less killing off inherent energy.

 

This point has NOTHING WHATSOEVER TO DO WITH CROSSWIND TECHNIQUES. Nothing to do with crabs or slips or sideslips! You can do all that stuff as recommended as a separate issue. Although diagrams in http://en.wikipedia.org/wiki/Crosswind_landing#Techniques from Boeing show that a literally crabbed landing is silly (= crash landing)... you want a de-crabbed one or side slip.

 

If you just do a search on videos about forward slip, demo's come in all languages. It isn't a localized technique or term. A forward slip can be distinguished by the pilot looking forward thru the SIDE window. A side slip may involve similar cross controls, but is done with the pilot looking out the FRONT window to see the same oncoming ground rush.

 

Here is a ground view of an extreme parachute-like forward slip. He comes down almost sideways, in spite of no crosswind.

 

 

Here is the case of the Boeing 767 that used that technique in an emergency landing w/o flaps or power http://en.wikipedia.org/wiki/Gimli_Glider "Pearson decided to execute a forward slip to increase drag and lose altitude. This maneuver is commonly used with gliders and light aircraft to descend more quickly without increasing the already-too-fast forward speed."

 

Here is video of a german sailplane demonstrating the usage of forward slip to prevent him from plowing into the hangers at end of airfield. I can't read the german caption, but I imagine it reads "thank god the Mosquito pilots didn't know how to do this, or there would have been even more overhead that we couldn't shoot down in the war. Their sorry manual just says if the flaps dont work, you only can come in too fast and pray".

 

 

Here is an italian video showing forward slip, with the caption "Eurofly Firefox forward slip to land practice, multiple view, Obiettivo Volare Airlfield, Fontanellato (Pr) Italy. This maneuver is used to reduce the height during the approach without increasing the speed. Is very useful in case you realize to be too high on the approach, or in case of an emergency landing out from the runway It is different from the side slip which is used to keep the plane straight on the runway during an approach with crosswind."

 

Note you have to replace the first x with h because this forum can't handle more than 2 videos per post. xttp://www.youtube.com/watch?v=LKyFh3wX0Q0"]

 

Here is a video showing forward slips being learned second day of US pilot training. xttp://www.youtube.com/watch?v=KoPqkUqvWBM"]

Here is a video where towards the very end a pilot shows a friend forward slips and how they were a lifesaver when his flaps didn't work (think about losing power as well). Nothing to do with crosswinds! xttp://www.youtube.com/watch?v=B3-Lu0EKSmQ"]

 

To bring it back to Asiana crash, I was trying to reverse the knee jerk dialogue about their plane coming in "too low". Oh, dear if they just would come in higher. But they intentionally played around by coming in too high. That meant they only needed engine power at the last second. Instead they could have come in normally lower, and sooner found and fixed the lack of power. Or to be super safe, come in even higher and not needed engine power at all... just forward slip to burn the energy off. All to do with energy control, not expecting power to be there at the last second like so many pilots

Edited September 1, 2013 by caesar novus

[caldrail]

Stop ujsing the phrase "forward slip". It isn't stabndard nomenclature.

[caesar novus]

Where is the list of standard nomenclature? There are 3 kinds of slip... generic (= accidental), side , and forward. Sometimes all of them are just shortened to "slip", because in context you know which one. It's conceivable that a lot of pilot communities lump a forward slip under "sideslip", but I question whether they comprehend the crucial forward slip mode. Maybe a third of world pilots don't know forward slips, another third knows them under that name, and another third lump them in with side slips.

 

But why impoverish terminology, when the point is to revive the use of forward slips? Some think they are obsolete due to the use of flaps or spoilers, but they have the advantage of being able to modulate instantly. Turn it on, cut it back, increase it... much faster than cranking a flap motor (assuming it works). There are some minor drawbacks such as wear on the rudder linkage, unreliable airspeed readings, or shuddering of the aircraft, but it's fine in an emergency mode.

 

Here are diagrams that distinguish the very crucial difference between the forward vs other slips:

 

click here ->

 

 

[caldrail]

Seriously mate, do have a problem with spacial relationships? Those two diagrams are exactly the same! Hilarious.

 

Well, despite living and breathing aviation as a child, flight theory and tests as a teenage air cadet, practical experience with motor gliders and military trainers, continued interest in aviation literature both historical and instructional, training as a private pilot successfully in both Great Britain and New Zealand, not until this ridiculous thread have I ever heard anyone use the phrase "forward slip" in connection with flight.

Of the pilots I had dealings with over the years from various countries, many were far better qualified and experienced than me. One of my instructors was a second world war veteran. I had the privilege of flying with a gentleman who had flown warbirds for the film industry, and with another who was the chief test pilot for light aircraft for the CAA. I often had conversations with a gentleman who flew business jets. None of them ever mentioned "forward slip".

I've done my time at the controls of real aircraft as pilot in command. Like everyone else who handles aeroplanes in the real world, I've had to conduct flights which challenged my skills either because of my own mistakes or because weather, circumstance, or technical issues made things difficult. In one case, a pilot I had conversed with a few times at the hangar met all those challanges at once and died in a tragic accident along with his passengers. That's reality. Flying is an activity that takes place in a very unforgiving enviroment. That's why I don't place much faith in self professed internet experts or the wannabee crowd on flight sim forums.

Since you haven't taken any notice of what I've said so far it's a safe bet you haven't any intention of doing so. I'll make sure I don't fly with you. But in the meantime, please don't bother trying to lecture me on sideslip. You haven't the slightest idea what it means nor the people you're getting this rubbish from. So I guess I won't be taking any notice of this thread any more.

[caesar novus]

There is a reason those diagrams have different orientations... the runway is at the top. See the click-here picture for description in words of how it is far more than an orientation issue. My point is overwhelmingly documented, and I have cited but the tip of the iceburg... you have shown no such documentation, but mainly rude bluster.

 

Pilots are on the whole unreflective and overly satisfied with their own provincial modus operandi... they kind of need to be because the priority is for decisive quick actions even if they are suboptimal. To rise above the mass produced student herd, try a dozen no-flap, no-power landings on a short field. You will be embarrassed that your went on this anti-intellectual jihad for something that is a lifesaver.

 

It would be a lesser evil if the pilot community accepted the maneuver of forward slip, but left it under a confusing ambiguous name of sideslip. That is, they employ it with NO crosswind and are looking directly down the runway thru their SIDE rather than front window due to massive rudder input. But I don't see evidence of that, just denial and ignorance abounds. And of course it is a larger issue of needless pilot assumptions that their engine or flaps will get them out of landing troubles. An informed and open minded sector of the pilot community knows and practices ways around those dependancies.

Edited September 3, 2013 by caesar novus