ATP forward slips
Posted by StageMajestic613@reddit | flying | View on Reddit | 89 comments
Low time student pilot here. Do you ATP folks flying those jumbo planes do forward slips? Or rather just use those additional control surfaces, not found in GA, for rapid energy loss?
I assume a forward slip would freak the passengers out with the uncoordinated movement?
Are you essentially always on an ILS glide slope from far enough out that energy management is much finer?
Mrs_Fagina@reddit
Just be a man and throw the gear
SP_Aman@reddit
No, unless you wanna have a chat with the chief pilot on ADM. Check this thread out.
StageMajestic613@reddit (OP)
Thanks, good read. I was at an EAA meeting last night where someone was saying slips beyond so many seconds were prohibited in their GA plane due to fuel starvation; the thread mentions that.
Gutter_Snoop@reddit
Slipped a Cessna 210 with full flaps and the wrong wing down. When I rolled out of the slip I didn't have power. So yes, it is absolutely a thing that can happen.
Far_Top_7663@reddit
I call BS on that. Not the fuel starvation / engine out, but the slip with the wrong wing down. That's physically impossible. When you slop you apply rudder in one direction and lower the opposite wing to prevent that the plane turns in the direction you are applying rudder. Bank towards the rudder and you are not in a slip, you are in a skidding turn.
HotPast68@reddit
I presume the wrong wing in this scenario would be a wing lower on fuel resulting in the starvation
Far_Top_7663@reddit
That could be. If u/Gutter_Snoop confirms it I will delete my comment.
Gutter_Snoop@reddit
Hotpast is correct.
The C210 has selectable fuel tanks. If you are, say, dipping the left wing down with right rudder, the fuel in the left tank likes to deposit itself at towards the tip of the wing, well away from where it gravity feeds.
So when you slip it when your fuel is lower than ~10 gallons, it behooves one to make sure you are feeding out of the tank on the "up" wing.
Far_Top_7663@reddit
Thank you. I will not det delete my original comment because that would also remove this explanation from you which I like and can be useful for others, but I will edit my original comment. Apologies for the misunderstanding.
Gutter_Snoop@reddit
All good sir or madam. My original comment was probably not worded as well as it could have been... although you probably didn't have to go full nuclear with declaring "bullshit" right out of the gate
Far_Top_7663@reddit
You are right, I should not have done that. I took the first interpretation that came to mind and kept building momentum on it, kind of confirmation bias I guess. I apologize.
fgflyer@reddit
They’ve got speedbrakes for energy management. Slipping a swept-wing aircraft is not a good idea.
N420BZ@reddit
For what it's worth, speedbrakes are also very rarely used on approach. All of my airlines have strongly discouraged speedbrakes with flaps extended (and prohibited beyond the first detent).
ThatLooksRight@reddit
I use speed brakes all the time. When ATC keeps you high and dumps you at the last minute, or Chicago is doing 14 speed changes, yeah, I’ll use them.
There’s just no other good option a lot of the time.
OccupyMyBallSack@reddit
ATC screwup gets max 1/2 boards. My screwup gets full boards.
Neither-Way-4889@reddit
"I need you to slow from 250 to your final approach speed in 3 miles"
Striderrs@reddit
The 737 needs 8 miles to do that with maximum effort slowing according to the books 😭
Gutter_Snoop@reddit
Many airplanes simply won't let you extend flaps with the speed brakes out or vise versa
kingcarlyshayster@reddit
That’s not true. On the citation I fly, speed brakes should be retracted 50 above touch down. We fly with speed brakes out on approach and final when we are running engine anti ice. We do this because we need power from the engines to power the system
Gutter_Snoop@reddit
Ok, some jets won't. The Phenom line, for example. Pretty sure some of the Citation airframes do too.
More_Than_I_Can_Chew@reddit
I flew a Jurassic jet at one point that basically required speed brakes out in the landing configuration to keep the leading edges hot enough in icing conditions.
A total handful.
Flimsy-Ad-858@reddit
I wouldn't say "many". The only one I can think of is the Hawker offhand.
DirtyEtzio@reddit
The Hawker will "let" you (physically).
It's just a lawyer-limitation.
Flimsy-Ad-858@reddit
As I recall the 900XP had a physical blocker where you could extend the airbrake out of stowed if the flaps were past 0. Except on the ground for the full lift dump. Am I misremembering that?
DirtyEtzio@reddit
Not seen that on any Hawker I've ever flown, but doesn't mean there's not one out there, I suppose.
Gutter_Snoop@reddit
Mmkay, many newer aircraft.
CMDR_Winrar@reddit
220 is the newest, no restrictions on flaps+spoiler use, just stable gates that prohibit spoiler, and automatic spoiler retraction based on thrust lever angle.
irishluck949@reddit
175 closes them automatically in a few conditions
Flimsy-Ad-858@reddit
Sure, the 220 does as well, but they're not limited by flap position. At least not directly.
irishluck949@reddit
Well the 175 is, flaps more than 1 and the brakes close
Flimsy-Ad-858@reddit
Ah okay it's been like a decade since I've done anything 170 related
DoomWad@reddit
That's not true. All of the jets I've flown, you can extend the speed brakes with the first couple notches of flaps. The flap detent where the gear must be extended before selecting it, that's usually the flap/speed brake limit.
Example: on the 737, the gear must be extended before selecting flaps 15. So, any flap setting prior to 15 you can use the speed brakes.
oldmate52@reddit
why?
Lazy_Tac@reddit
It’s prohibitEd in my flight manual. Talks about loosing panels
oldmate52@reddit
You probably don't need all the panels
Gutter_Snoop@reddit
Because it's a great way to stall your wing.
JustDaveIII@reddit
After coming over the mountains into ONT on SW late February, speed brakes were definitely used to get us down. I was sitting where I could see them.
More_Than_I_Can_Chew@reddit
Passenger comfort or airframe comfort?
Various-Blood-3902@reddit
Yes
DoomWad@reddit
I mean, we do side slips when landing. Forward slips are a no-no though
Various-Blood-3902@reddit
Why?
Tryptamine91@reddit
The wing on the side of the aircraft opposite the relative wind generates almost no lift because it’s blocked by the fuselage.
Double_Combination55@reddit
Depends how you define a good time…. But jokes aside. Swept wing , slow, low, and slipping is a recipe for code brown
Student_Whole@reddit
Everyone says this, without much education. Swept wing aircraft slip just fine if done correctly. Is it the best option? No. Does it work? Yes. Are there issues you need to be aware of and mitigate while doing it? Yes. If you roll or spin when slipping, it’s because you were doing it wrong, not because it’s a bad maneuver.
22Planeguy@reddit
It's a bad idea because it requires a lot more precision to do safely (which, imo makes it inherently unsafe), which introduces risk that is completely unnecessary and antithetical to the concept of ADM. There are so many reasons not to try to slip a large jet and zero reasons to try to that can't be solved safer by going around and trying again.
__joel_t@reddit
Except the rare cases where a go-around isn't possible (the most famous example being the Gimli Glider).
PuzzleheadedDuty8866@reddit
When you’re going that fast and have that big of a rudder, the tail could break off. It’s a warning in the C-5 manual
DanThePilot_Mann@reddit
Not forward slips. But side slips are utilized in ground effect on nearly every airliner. (Some are designed to land in a crab).
Note, we don’t start side slipping at 500 feet, like I hear some CFIs teach. We take the crab down to less than 50 feet, then kick the rudder for centerline allignment and ailerons to prevent side drift. (This is something you honestly should be doing in all airplanes, even in training)
phliar@reddit
You don't slip swept-wing airplanes.
DoomWad@reddit
You don't forward slip swept-wing airplanes. Side slips are done on crosswind landings.
More_Than_I_Can_Chew@reddit
Side slip for a side wind :)
Bluzzard@reddit
Is this why I see airlines crab instead of doing the wing low side slip?
ma33a@reddit
No that's more to do with avoiding scraping the engine on landing.
cirroc0@reddit
Not even the Gimli glider?
320sim@reddit
There’s exceptions to every rule. Especially when you have complete loss of power and have one shot to land
fgflyer@reddit
It also helped that the captain on the Gimli flight had a significant amount of experience flying gliders, and was thus excellent with energy management. At least from what I recall about the incident.
AndyTheEngr@reddit
I visited the museum in Gimli. Really cool!
NeedMEI@reddit
You can if you understand the aerodynamics. A slip isn’t certain death. Of the wing isn’t loaded and you have a buffer it’s just like doing it in a 172.
Small_Chicken1085@reddit
And where did we learn this?
Student_Whole@reddit
Yes, you can. Just don’t do it with low airspeed. Which would be a real stupid time to slip anyway right?
StageMajestic613@reddit (OP)
Ah, thanks!
JPAV8R@reddit
We use the drag devices up high. An approach requiring a forward slip to a landing would be unstable in a heavy jet. Think of the inertia involved in a 300,000kg jet. Imagine you get that forward slip wrong.
Additionally on some jets a forward slip could starve an engine of air if its air source is blocked by the fuselage and you could reduce the control effectiveness of a control surface if you block the relative wind to it.
Overall is just a bad idea. On transport category aircraft it makes sense to start your decent towards a landing fully configured, on your approach speed, and let the way the plane (and approach) was engineered work for you.
ghjm@reddit
Even in a light GA plane, doing a forward slip to landing generally means you screwed up descent planning at an earlier stage of the flight. It's important as a student pilot to know how to do it, but you won't likely be using it much as you proceed through your training and flying.
Effective-Scratch673@reddit
Wrong. It's a very needed skill to have in your repertoire as a Commercial and CFI applicant when doing Power Off 180s, one of the maneuvers where pilots struggle the most during checkrides. And of course for emergencies
KITTYONFYRE@reddit
it’s useful for energy management coming into small strips or strips with obstacles you want to drop down behind, too - not JUST for when you mess up by being too high!
JumboTrijet@reddit
Except one should be proficient at forward slips in case it’s needed for an engine failure.
jjamesr539@reddit
Speed brakes and spoilers. An aggressive forward slip would be incredibly uncomfortable for passengers, could be hard to control given the swept wing, could induce oscillation that exceeds structural capacity, could induce compressor issues for the turbines if held, and has all sorts of implications for stalls and spins with a swept wing and leading edge devices. Jets with swept wings have stick shakers and pushers for very good reason.
ThatLooksRight@reddit
Yaw damper. Not dampener.
Cessnateur@reddit
You're being downvoted, but despite some manufacturers opting to use "dampener," "damper" is, in fact, the less ambiguous and more correct term.
TripNo1876@reddit
At this level you should be on profile and speed with minor corrections so something like a forward slip is not needed.
andrewrbat@reddit
You don’t want to side slip jets with swept wings. The only time you would intentionally slip a jet is the last 30 feet or so, during a cross wind landing. Intentionally putting a swept wing jet into a slip and sometimes result in Dutch roll oscillations. You also put one of the wings into an aerodynamic shadow and that way will also have its effective sleep angle increased, even more reducing lift. At low speed this is not a good thing to have happen.
jet-setting@reddit
The Gimli Glider has entered the chat
There’s a very famous case of performing a forward slip on an airliner, and more or less one of the only times it’s been done. If a jet is not on a stable approach, it’s a go around.
The “Gimli Glider” was a brand new 767 that ran out of fuel over the middle of Canada in the early 1980’s. The crew did a phenomenal job finding a suitable landing option (a decommissioned air force strip), but they had a bit too much energy and the Captain performed a forward slip as a “nothing left to lose” maneuver.
F1shermanIvan@reddit
If the crew had done a real phenomenal job, they wouldn’t have run out of fuel halfway to their destination and taken an unairworthy aircraft into the air.
But hey.
ElPayador@reddit
LBs to Kg is very difficult math 🤪
jet-setting@reddit
Not disagreeing at all to what you’re saying. They got lucky as fuck.
Flying the plane well doesn’t absolve them from the fuckups that created the problems in the first place, but they did at least fly the plane well.
Exotic-Sale-3003@reddit
Yeah, plans don’t run out of gas nearly as often these days. I’m sure the pilots have gotten smarter and it has nothing to do with the safety systems that surround them.
F1shermanIvan@reddit
No, but the crew might have done the math properly, not disregarded the MEL that said you can't take the aircraft airborne with no fuel gauges, noticed that the V speeds didn't make sense for the weight the aircraft was supposed to be at, etc...
You know, actual pilot stuff we're supposed to do.
More_Than_I_Can_Chew@reddit
Well I guess they didn't have to worry about an engine flaming out.
Ok-Selection4206@reddit
Thats what I was thinking, slipping a big jet is a great way to save fuel when you blank an engine out.
M2K-throwaway@reddit
?
BeenThereDoneThat65@reddit
The ONLY reason they got away with the slip was because they had no other option
swakid8@reddit
Only in the simulator…..
Not something I would in a swept wing airplane unless it’s all or nothing like the Gimli Glider…
But we have speed brakes, flaps, and gear. If I am on approach and need to slow and the aircraft is having a hard time slowing, drop the gear.
ozzies_35_cats@reddit
This is how you bend things.
MEINSHNAKE@reddit
Biggest thing I’ve put into a forward slip was a king air… wasn’t particularly comfortable or necessary.
bergler82@reddit
ar a former airline of mine there was this story about a captain that slipped a 757 many many many moons ago. Plane was supposedly bent beyond repair.
legitSTINKYPINKY@reddit
My pax wouldn’t like that😂
BrtFrkwr@reddit
Not unless you want to pull the job change circuit breaker.
Pseudo-Jonathan@reddit
You need to be much more deliberate and anticipatory about energy management in jets. You can't just slow down on a whim. And you can just forget about descending and slowing down at the same time. No you cannot pull any fancy moves like slipping. You just need to control your energy in advance. If you fail to do so, you'll need to go around.
rFlyingTower@reddit
This is a copy of the original post body for posterity:
Low time student pilot here. Do you ATP folks flying those jumbo planes do forward slips? Or rather just use those additional control surfaces, not found in GA, for rapid energy loss?
I assume a forward slip would freak the passengers out with the uncoordinated movement?
Are you essentially always on an ILS glide slope from far enough out that energy management is much finer?
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