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Engine failure video

Old 11th Nov 2021, 05:47
  #101 (permalink)  
 
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If something you're doing in the plane is different than what the POH says, it's not approved
Good advice from DAR. Cessna 172H POH - Slips are prohibited in full flap approaches because of a downward pitch encountered under certain combinations of airspeed and sideslip angle. (Presumably 30° is OK as full flap is 40°)

172S on the other hand says - Steep slips should be avoided with flap settings greater than 20° due to a slight tendency for the elevator to oscillate under certain combinations of airspeed, sideslip angle, and center of gravity loadings.

Why? Quote from a DAR post elsewhere, source "Cessna, Wings for the World" by Cessna test pilot William Thompson.
With the advent of large slotted flaps in the C-170, C-180, and C-172 we encountered a nose down pitch in forward slips with the wing flaps deflected. In some cases it was severe enough to lift the pilot against his seatbelt if he was slow in checking the motion. For this reason a caution note was added in most of the owner's manuals under "landings" reading "slips should be avoided with flap settings greater than 30(degrees) due to a downward pitch encountered under certain combinations of airspeed, sideslip angle, and center of gravity loadings"......Although not stated in the owner's manuals, we privately encouraged flight instructors to explore these effects at high altitude, and to pass the information to their students.......When the larger dorsal fin was adopted on the 1972 C-172L, this sideslip pitch phenomenon was eliminated, but the cautionary placard was retained.
So if you fly an A to K model 172 you could be in for a surprise.

Difference in dorsal fin.

172K


172L

Last edited by megan; 11th Nov 2021 at 06:04.
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Old 11th Nov 2021, 05:55
  #102 (permalink)  
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Originally Posted by megan View Post

One author has said in a typical Cessna 152/172/182, depending on the amount of slip, the airspeed can easily be off by 20%, which means the energy is off by 40%. This is enough to cause real trouble. Location of the static source induces errors.
Does it follow that it's more conservative to side-slip to the right if your static port is on the left of the aircraft? ie presenting the static port to the airstream will result in the IAS being lowered rather than raised ?
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Old 11th Nov 2021, 11:06
  #103 (permalink)  
 
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Doesn't the Cessna single engine fleet have a static port each side?
Also there are reasons to slip one way or another, wind direction, direction of engine rotation for example. The trick is to "ahem" use the correct attitude for the airspeed you want.
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Old 11th Nov 2021, 11:28
  #104 (permalink)  
 
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Doesn't the Cessna single engine fleet have a static port each side
The ones I'm aware of have only a single port on the left side.

db, with the Cessna and its left side static port I'd expect that a slip to the left would have the port seeing increased pressure, slip to the right reduced pressure. The question then becomes what does the pitot see? An academic paper says,
When the inclination of the flow exceeds about 15-20 degrees, significant errors will result due to the friction and boundary layer separation effects that occur. In these situations, the pressures sensed at the Pitot-static tube ports do not represent the desired stagnation pressure and static pressure. This is due to the fact that the Pitot-static probe is not a directional device, and so in unknown flow situations, a departure from the ideal uni-directional flow can result in very significant errors—errors which may be unknown to the observer due to lack of knowledge of the true flow direction.
The summation of all the effects you need to become a test pilot.
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Old 11th Nov 2021, 11:49
  #105 (permalink)  
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Cessna 150/152's have the static port on the left fuselage side only. All other Cessna's I'm aware of have at least two static ports, left and right, interconnected. Newer Cessnas with G1000 have four static ports. Any flying you do which causes an angle off approaching 20 degrees for the pitot tube or static port introduce noticeable errors. Interconnected static ports greatly reduce the effect on the static side of the instruments. Very specialized or swiveling pitot tubes reduce this effect for airspeed readings, but are generally not worth the trouble and expense.





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Old 11th Nov 2021, 11:56
  #106 (permalink)  
 
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Quite apart from discussing what the pitot 'sees' when side slipping and what forward speed pressure sensing it feeds to the ASI.compared to actual speed (during a sideway slip).
{I have my own pet theoriy !]
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Old 11th Nov 2021, 17:54
  #107 (permalink)  
 
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Originally Posted by Rozy1 View Post
Yes, there is a difference! Can you not see the picture?

Hint- look at the ground path and the angle between said ground path and the leading edge of the wing.
Sorry, but differentiating between forward slip & side slip is meaningless; even when forward slipping I'll aim to track towards a particular ground feature. Your diagram above is deliberately deceptive, the forward slip omits any wind effect & is clearly right rudder, left wing down, the side slip is left rudder, right wing down. What does the diagram mean by "flight path"? The forward slip part suggests that "flight path" = "heading before applying the rudder" but if we apply that definition to the side slip part then the heading before applying the rudder would be directly into wind, in which case the ground track/path would also be directly into wind. Adding some left rudder and right wing down won't change that. That is a very, very poor diagram.

Lets imagine I'm flying towards an airfield, there's a crosswind from the left so I have adjusted my heading so that my ground track is straight torwards my destination. When I start my descent I realise that I have left it too late & will be too high so I decide to add some extra drag by feeding in some right rudder, using left wing down to maintain my track towards the airfield. This is what you would call a forward slip. Fortunately the runway in use is aligned with my direction of travel, my descending forward slip is taking me down the extended centreline of the runway. It's a quiet airfield, I make the usual radio calls announcing I'll be joining straight in on to final approach & continue my right rudder, left wing down flight all the way down final, through the roundout & hold off until touchdown.

At what point did the forward slip magically transform into a side slip?
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Old 11th Nov 2021, 20:01
  #108 (permalink)  
 
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Originally Posted by Prop swinger View Post
Sorry, but differentiating between forward slip & side slip is meaningless; even when forward slipping I'll aim to track towards a particular ground feature. Your diagram above is deliberately deceptive, the forward slip omits any wind effect & is clearly right rudder, left wing down, the side slip is left rudder, right wing down. What does the diagram mean by "flight path"? The forward slip part suggests that "flight path" = "heading before applying the rudder" but if we apply that definition to the side slip part then the heading before applying the rudder would be directly into wind, in which case the ground track/path would also be directly into wind. Adding some left rudder and right wing down won't change that. That is a very, very poor diagram.

Lets imagine I'm flying towards an airfield, there's a crosswind from the left so I have adjusted my heading so that my ground track is straight torwards my destination. When I start my descent I realise that I have left it too late & will be too high so I decide to add some extra drag by feeding in some right rudder, using left wing down to maintain my track towards the airfield. This is what you would call a forward slip. Fortunately the runway in use is aligned with my direction of travel, my descending forward slip is taking me down the extended centreline of the runway. It's a quiet airfield, I make the usual radio calls announcing I'll be joining straight in on to final approach & continue my right rudder, left wing down flight all the way down final, through the roundout & hold off until touchdown.

At what point did the forward slip magically transform into a side slip?
That is not my diagram. Prove your point with documentation.

I am not arguing that in both you don’t cross control the same way. They do serve two different purposes and are semantically different, otherwise there wouldn’t be two different names. If you can’t understand this I don’t know what to say.

Deliberately deceptive? Seriously?

Maybe the FAA’s diagram is better:





Last edited by Rozy1; 11th Nov 2021 at 20:26.
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Old 11th Nov 2021, 20:06
  #109 (permalink)  
 
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Old Bridge landings

I have landed at Old Bridge a few times and like a lot of airports in NJ there are tall trees around. The trees get taller every year and the neighbors can object to getting them cut down so the impact can creep up on you. The tree line can also create some interesting wind patterns. Where I was based at Somerset it could be tricky when landing on 12. That end of the runway was in a box canyon of trees and the wind made a vortex. As you came over the trees the wind was often very different than the wind sock at mid field.
The result was keeping a bit high and fast on a long final was a good idea. I did my PPL in a 172 based in the area and was always shown to use S turns to bleed off speed and I did so frequently. It worked very well. Keep the nose pushed down and watch the runway picture. We did practice some slipping as well but I can't remember any limits on flaps. I do remember it was a very effective way to dump altitude in a hurry. It felt uncomfortable the first few times. A good skill to practice.
I can't find if it says how far from the airport and what height they were at when the engine quit. Does anyone know?
Was the plane based there?
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Old 11th Nov 2021, 22:40
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From the FAA airplane flying handbook:
A sideslip is entered by lowering a wing and applying just enough opposite rudder to prevent a turn.
From the FAA airplane flying handbook:
In a forward slip, ... the wing on one side is lowered by use of the ailerons. Simultaneously, sufficient opposite rudder is used to yaw the airplane’s nose in the opposite direction such that the airplane remains on its original flightpath.
Technically, there is no difference between a forward slip and a sideslip, in that they both require crossed controls. However, the purpose of each is different, in that the intention of the forward slip is to lose altitude without increasing airspeed while maintaining ground track and flightpath, even though the nose of the aircraft will no longer point in the direction of the flightpath, while the intention of the sideslip is to maintain aircraft heading and flight path, relying on a countering crosswind to maintain ground track - essential in landing to ensure that the nose is pointing straight down the runway, i.e. aircraft heading is aligned with flightpath to avoid drift and lateral loading on the undercarriage.

This is the "wing down" method of crosswind landing, as opposed to the "crab" method, where there is no crossed control, and the nose is pointed into wind so that the ground track is aligned with the runway - with the nose yawed to align with the runway just before touchdown. I've always been a crab man myself, but I'm a Cancerian, so it was written in the stars.
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Old 11th Nov 2021, 23:27
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Originally Posted by Fly-by-Wife View Post
From the FAA airplane flying handbook:
From the FAA airplane flying handbook:

Technically, there is no difference between a forward slip and a sideslip, in that they both require crossed controls. However, the purpose of each is different, in that the intention of the forward slip is to lose altitude without increasing airspeed while maintaining ground track and flightpath, even though the nose of the aircraft will no longer point in the direction of the flightpath, while the intention of the sideslip is to maintain aircraft heading and flight path, relying on a countering crosswind to maintain ground track - essential in landing to ensure that the nose is pointing straight down the runway, i.e. aircraft heading is aligned with flightpath to avoid drift and lateral loading on the undercarriage.
so what do you call it if you are high on final and are crabbing to maintain centreline and then decide to enter a sideslip to drop some excess height and in doing so align the aircraft's nose parallel to the centreline? a side forward slip maybe?

It is probably just me but I struggle to see the need to give a sideslip 2 different names when it is the same manoeuvre with identical control inputs. You can use it to lose height without speed or lose speed without gaining height or to assist an observer look out the window or whatever.

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Old 12th Nov 2021, 01:04
  #112 (permalink)  
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It is probably just me but I struggle to see the need to give a sideslip 2 different names when it is the same manoeuvre with identical control inputs. You can use it to lose height without speed or lose speed without gaining height or to assist an observer look out the window or whatever.
It's not just you, me too! I want to go there, but will cross control it and point it over there for a time, to best achieve that. The arrows and terms are of less consequence, if it was safe, and worked as intended!
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Old 12th Nov 2021, 01:14
  #113 (permalink)  
 
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Cessna 150/152's have the static port on the left fuselage side only. All other Cessna's I'm aware of have at least two static ports, left and right, interconnected
A check of the manuals I have 150, 152, 172 have single port, 182, 206, 210, 207 have dual. With the plethora of versions of a particular model Cessna built it would pay to check the particular aircraft you're about to hire.
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Old 12th Nov 2021, 07:15
  #114 (permalink)  
 
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A check of the manuals I have 150, 152, 172 have single port,
Too easy. Quite sure the Cutlass (172RG) has two ports
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Old 12th Nov 2021, 07:23
  #115 (permalink)  
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The 172M I fly has one, on the left. Which is why I was speculating that pointing the nose right of track might lead to reduced IAS due to increased static pressure, while perhaps the pitot would be less sensitive to direction. Although of course I'm sure it's not as simple as that and I would be foolish to do anything other than be aware the IAS will have increased error in a slip.

(just musing, just a thought experiment. Please don't haul me over the coals for inventing my own POH)
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Old 12th Nov 2021, 12:19
  #116 (permalink)  
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I'm sure it's not as simple as that and I would be foolish to do anything other than be aware the IAS will have increased error in a slip.
True, but still wise of you DB. I stand corrected that some 172's have only one port, and your observation, and reason for awareness are wise. That being said, when I slip, which is often, I'll fly with a reserve of speed anyway, so a possible position error will be less significant.
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Old 12th Nov 2021, 15:40
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How much "extra speed" then ?
And surely being a test pilot you'd have already checked at safe height various non straght ahead slow flight ASI readings to determine if your guess is near the mark or even valid ?
And what about the sideways air across the forward facing pitot effects ??
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Old 12th Nov 2021, 18:17
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Originally Posted by Rozy1 View Post
That is not my diagram. Prove your point with documentation.

I am not arguing that in both you don’t cross control the same way. They do serve two different purposes and are semantically different, otherwise there wouldn’t be two different names. If you can’t understand this I don’t know what to say.

Deliberately deceptive? Seriously?

Maybe the FAA’s diagram is better:
No, it isn't. It is just as hilariously deliberately deceptive as your previous diagram. In order to induce an artificial difference between the two supposedly different slips the FAA diagram omits the crosswind in the second picture and therefore has the aircraft flying an entirely different heading before slipping.

The FAA's fig 9-13 must have a crosswind from the left. That is the only way that the aircraft can be flying into the relative wind, ie direction of flight through the air, and still be tracking down the runway. In co-ordinated flight the aircraft heading would be directly into the relative wind, the pilot then feeds in some right rudder and left wing down and the heading is now aligned with the track over the ground. Fig 9-14 deliberately omits any crosswind, in order to track down the runway the aircraft is flying down the runway. If the crosswind implicit in fig 9-13 was added to fig 9-14 then to track down the runway the aircraft would have to fly slightly into wind to compensate for the crosswind, in other words the airflow/relative wind would come from the left of the runway, as in fig 9-13. When the pilot adds some right rudder and left wing down to 'forward' slip fig 9-14 would look identical to fig 9-13.

To put it bluntly, the difference between the two images in the FAA handbook is not that the aircraft is flying two distinct, different manoeuvres but that one image includes the effect of a crosswind, the other image does not. That's it. They are only semantically different because someone chooses to make them so, it reminds me of the asinine distinction between gliders and sailplanes that some US glider pilots like to make. If you want to carry on making the distinction, help yourself, but don't come on to an international forum and start lecturing people "that's not a sideslip, that's a forward slip" and expect not to be laughed at.
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Old 12th Nov 2021, 18:24
  #119 (permalink)  
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How much "extra speed" then ?
Qualitative, rather than quantitative. I'm certainly not slipping to fly slowly, so if the slip is achieving what I want it to, that's good enough for me.

checked at safe height various non straght ahead slow flight ASI readings
The safe height for this is desk height, before flight, as it's a review of the flight manual position error correction table, for the intended speeds - but knowing that if the airplane has any aerodynamic modifications, the position error correction table in the original flight manual is probably no longer correct. Once you're airborne, there is no way to know the difference IAS to CAS unless the aircraft is instrumented for it.

Yes, I have tested a number of aircraft with the swiveling pitot static head (photo posted earlier in this thread). That is one of the few ways to gather position error data for an aircraft. On my 150, I was able to measure IAS to CAS errors as much as 19 MPH in high AoA and slips. I've used it on a number of modified aircraft. It's particularly useful on helicopters during autorotation, where there is no other means to determine position error. There's also a GPS method, usable in precise level flight, but hardly useful in high AoA, or power idle flight.
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Old 12th Nov 2021, 19:21
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Thank you DAR,

But what is your experience/opinion on slow slipping finals ASI when the PITOT has the airstream skiddig partially sideways acrtoss it. And as a corollary what that means for wing lift at that configuaration & velocity ?
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