F152 sideslip with flaps

[tmmorris]

Can one sideslip a Cessna F152 (1980 model) with flaps extended? Couldn't find a reference in the (non-indexed) POH/FM.

Thanks,

Tim

[Barnstormer1982]

You may not in C150s, C172s, C170s, so I would assume that you may neither in C152s. Not having flown a 152 / not having read the manual, this is pure assumption of course.

[fallen eagle]

I think its more a question is it necessary?A 150 or 152 will perform a very respectable side slip without flaps.Best done lowering the left wing so as not to cause erroneous air speed indications by shielding effect of the pitot and static vent if you lower the right wing.The power of the 150,40 degrees negates any need for side slip and poses two problems 1,shielding of and loss of rudder control 2,uneven load on left and right flap if you wish to know what uncommanded asymetric flap retraction in level flight is like I can tell you its not pleasent.Let alone loosing the left flap in a slip to the left.Though the 152 flaps are slightly less effective choose your approach, flaps and no side slip, or flapless with slip if needed.As always available runway and wind conditions taken into account. However there are some aircraft where the combination is approved and is so stated in the flight manual.

[MichaelJP59]

Does this mean that in a Cessna 150/152 a cross-wind wing down type of approach should always be flapless?

- Michael

[fallen eagle]

I think there is a world of difference between a side slip and a wing down approach.Cessna 150 x/wind.DEMONSTRATED performance not limit as there is not one published,is 20 mph take off 15 mph landing at 90 deg.C152 12 kts take off and landing.reduced performance due to taller fin and rudder causing weather cocking.I would agree if the x/wind is near demonstrated performance, or limits ,and more important the pilots personal limit then the wing down method is a good option,but to be successful it requires very accurate handling close to the ground.The more common crabbing teqnique seems to be quite successful so long as the intowind aileron is applied as the a/c is yawed straight.So how about normal crabbing method till the flare then into a gentle wing down.This can be flapless or with flaps dependant on runway available and if marginal, increased likelyhood of a go arround.

[MichaelJP59]

I seem to find it easier to transition to wing-down on the final approach from further back, say 200ft alt. as I am then used to the control inputs needed to keep the attitude correct through any gusts.

Leaving it until the flare then applying rudder and aileron along with the elevator required seems harder to me.

Sorry about going o.t. with respect to the original question!

- Michael

[fallen eagle]

Michael I dont think you were OTT.Perfectaly reasonable question and if you are comfortable doing it the way you describe and getting settled that sounds good.I can only reiterate that a wing down maybe 10-15 deg max is going to be much less than a good sideslip where you would be almost be looking along the leading edge to see your landing area.Anyway its all about chatting, dissemination of information and opinions.Main thing is to keep safe and within our own personal limits.Now we have taken this thread from sideslipping a C150 through X/wind techniques lets see where goes from here.HA! I have been away too long.Martin

[Tinstaafl]

Slips with flap extended are not prohibited by Cessna. Cessna recommends they should be avoided. Not the same thing at all.

If slips were prohibited you would not be able to do wing down x-wind landings. Cessna's own pilot training system of the 70's/80's used the wing down method.

[FlyingForFun]

Someone please correct me if I'm wrong here, but, as Tinstaafl says, Cessna recommend avoiding sideslips with flaps for certain models of C172 - I seem to recall the Millenium edition C172 falls into this category. It's been a year or so since I last flew one of these, so I may be wrong, but I seem to recall the recommendation actually only applies to full flap?

However, I'm not aware of any C150/C152 manual which mentions the issue at all, and I also don't believe that the earlier C172 manual mentions it either. I will certainly have another look through the manuals at work tomorrow (we have a selection of them covering models from 1950s through to 1980s, not sure if we have the F model manual or not).

To my mind, if the manual does not explicitly proclude me from carrying out anything which is considered normal aviation practice (and I would argue that sideslips are normal aviation practice) then it is ok to carry out that practice. So I would suggest that sideslipping a C150/C152 either with or without flap is a perfectly legitimate thing to do.

FFF
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[tmmorris]

Thanks all - yes, it was precisely wing-down landings I had in mind. I've been trained resolutely to crab, but wanted to try wing-down, and wondered if the C152 was a good place to start. Apparently so, but perhaps with less than full flap.

Thanks all

Tim

[S-Works]

side slip mine all the time at various stages of flap. nothing in my POH about not doing it and in a thousand hours nothing has fallen off yet!

[NorthSouth]

tmmorris:it was precisely wing-down landings I had in mind. I've been trained resolutely to crab, but wanted to try wing-down, and wondered if the C152 was a good place to startNo reason not to. I fly 152s regularly and always use wingdown in our all-too-frequent x-winds. My normal practice is a transition from crab to wingdown at about 200ft because wingdown usually involves a change in pitch attitude as the additional drag of crossed controls slows the aircraft down. But hey, it's all in the last 3 seconds.....

and, I meant to say, I do wingdown with full flap or 2 stages depending on gust conditions, just the same as if the wind was straight down the tube.

[Sunfish]

All I know is that side slipping a C150 with flaps extended is a no- no at least in our operating manual. I'm told it is because it can interfere with tailplane airflow causing a major pitch down (or is it up?) response - Fallen Eagle has it right.

However side slips and wing down landings are different things, we are taught that wing down is the preferred method of landing a C150 in a crosswind.

I'll have a look in the operating manual tomorrow and see if I can find a reference.

[Tinstaafl]

Sideslips & the wing down x-wind method are not two different things. As far as the airframe is concerned they're aerodynamically the same.

Something I've noticed for many a/c types is that the x-wind limit is also about where full rudder is required to maintain alignment while tracking the centreline at landing speeds. Always wondered if that was a consideration when the manufacturer determined the x-wind limit. Of course it's possible to use additional techniques to land in stronger x-winds but it's an interesting thought.

[2Donkeys]

WR has given you the answer. This has nothing to do with 152s at all. Slip all you like.

2D

[Genghis the Engineer]

I agree completely with TINSTAFL, a wing-down landing is simply landing in a steady heading sideslip. Nothing wrong with that - but the only difference between that and a sidelipped approach is how high you are above the ground.

I'd have only one concern doing this with a 2-seat high-wing Cessna, which is that many of them only have a single static, on one side of the fuselage. The means that in sideslip you'll get siginificant ASI (and altimeter) under or overread (depending upon which way you are sideslipping). This is not a problem per-ce, but means that the aircraft MUST be flown by visual cues and attitude, and not by reference to instruments. Which, let's be fair, is what we should be doing anyway :}


It isn't permitted for an aircraft manufacturer to limit sideslipping for structural reasons - the safety requirements are very clear on this point. However, some aeroplanes will potentially become unstable when sideslipped (particularly near aft CG) with flaps down. This may be in either pitch or yaw. I believe that this is the reason for the prohibition on full flaps sideslipping in some models of C172, but not having ever worked on the type, I've no idea what the specific instability is.

I did once manage the certification of a similarly configured aeroplane to a C152, which would become unstable in pitch (quite alarmingly so) with full flaps and near to the aft CG limit. We solved this by prohibiting use of full flaps with anything in the rear baggage compartment. This was a gross simplification of what was really happening, but ensured that the pitch stability would never be met - I imagine that the same was done with the 172. (Which would explain why some pilots have proudly said that they have sideslipped a C172 with full flaps without problems, I think that they didn't quite get into the particular weight/CG/speed/flap setting combination that some report buried in the Cessna archives will tell us causes the problem.)

G

[MichaelJP59]

I'd have only one concern doing this with a 2-seat high-wing Cessna, which is that many of them only have a single static, on one side of the fuselage. The means that in sideslip you'll get siginificant ASI (and altimeter) under or overread (depending upon which way you are sideslipping). This is not a problem per-ce, but means that the aircraft MUST be flown by visual cues and attitude, and not by reference to instruments. Which, let's be fair, is what we should be doing anyway

Interesting... I wonder by how much the ASI will vary. I think I'll experiment next flight by noting the variation in co-ordinated and side-slip conditions.

- Michael

[Tinstaafl]

It's not a prohibition in Cessna. In all the Cessna manuals I've seen that include a slip limition the language used is '...should be avoided' (sometimes 'extended slips...'. This is a distinctive language change compared to other limitations given in the same manual(s) where 'must' or equivalent gets used.

[Sunfish]

I looked for it in the Aerobat manual today and couldnt find it. I asked an instructor who made the comment that prolonged sideslipping could uncover one of the fuel strainers in a 172 fuel tank, and if thats the one you selected - tough.

Hope this helps.

[djpil]

My copy of the POH for a 1958 model Cessna 172 prohibits sideslips with full flap due to sudden pitch down that can occur at certain airspeed/sideslip combinations. Some years after that the text changed to this (in some that I have seen): "Steep slips should be avoided with flap settings greater than 20deg due to a slight tendency for the elevator to oscillate under certain combinations of airspeed, sideslip angle and center of gravity loading." I don't know the reason for the change. There may be other variations in POH's for different models and I'm not familiar with the new ones.

From my Cessna 150 POH - no restriction on sideslips.

The Husky can also pitch down suddenly at a certain flap/power/airspeed range - if it is orbiting and meets its own slipstream. The horizontal tail stalls so quite a sudden pitching motion.

[Tinstaafl]

The change in wording is most likely as a result of the various empenage modifications Cessna made over the years to the C172 eg enlarging the tailplane & extending the dorsal fin. I read somewhere that the dorsal fin extension had a significant effect.

['I' in the sky]

A long time since I've flown a 152 but I did my PPL on one and also a good chunk of my hours building.


The POH for the 152 as far as I remember made no mention of not doing sideslips with flaps extended and I do remember during my training doing some quite steep sideslips with flaps extended and having no problems. Note of caution - just because somebody says I've done this x times or for x years and it's never gone wrong doesn't mean they haven't just been lucky so you should check the POH for yourself and I stand to be corrected.

However regarding the application of sideslip to wing down crosswind landing technique, the 152 is one of the few manuals I've come across which DOES recommend that you consider using a reduced flap setting for crosswind landings.

Tinstaafl, I've never come across a POH yet which quotes a crosswind limit, just a maximum demonstrated crosswind component. The reason for this as explained by a manufacturers certification test pilot is that the manufacturer isn't going to go to the time and expense of conducting test flights purely to investigate the aircrafts crosswind limit, so the quoted maximum demonstrated crosswind component is simply the maximum which they happened to encounter during flights testing other performance data.

However you sort of answered your own question. The real crosswind limit of the aeroplane is when you have used all available rudder authority to prevent the yaw induced by lowering the wing, ie at full rudder deflection.

[Tinstaafl]

'I', yes I realise that. I was more musing on the (coincidental?) match with the demonstrated x-wind limit.


WRT to their recommendation to reduce flap in a strong x-wind, it need not be slip related. Reduced flap means slightly faster landing speeds --> greater control effectiveness and also reduced drift --> reduced control inputs needed to counter the wind effect etc.

When working in the Shetlands and elsewhere I was often landing in 40+kts of x-wind. Reduced flap was one part of getting it on the ground in the conditions.