Hydraulic failures

[PA Pilot]

I'm about done with my transition from the R22 to the R44. One of the things we worked on was run on landings with failed hydraulics.

 

Since my only experience with helicopters with hydraulic assisted controls is the R44, my question is:

 

When hydraulics are turned off in a hover, is the R44 typical of all helicopters in the amount of play (feels like a foot, but probably more like 1/2") in the cyclic? It struck me like trying to learn to hover all over again...

[joker]

Squirrel - From what I've heard the squirrel becomes very hard to control. Some weaker people may not even be able to do it.

 

S76C+ - You've no chance! Impossible to move controls without it. Need hydraulics muchly! Also, if you lose hydraulics you may not be able to put gear down, unless you blow them down with emergency blowdown gas. Fortunately, there are 2 independent systems.

 

Joker

[Gomer Pylot]

I've never flown a Robbie, so I can't say if it's typical, but it sounds like a lot. The AS350 is fully controllable without hydraulics. We used to practice approaches to a hover, and then a full landing, hydraulics off. It's certainly hard to move the controls, but you don't need to move them a lot if you do it right. No medium helicopter I know of, except for the UH1, is flyable at all without hydraulics. That's why there are two redundant systems, and the loss of one requires a landing as soon as possible. It's also impossible to turn off both systems at the same time. We used to land the UH1 with the hydraulics turned off, too, because there was only one system. It's a handful, but if you're young and desperate, it can be done.

[delorean]

B206 is easier to fly w/o the hydro's than the R44. I can't remember what the B47 was like w/o them.

[Goldy]

B206 is easier to fly w/o the hydro's than the R44. I can't remember what the B47 was like w/o them.

 

 

I havent done any R44 time, so I cant compare...but the Bell47 is like flying a brick without hydraulics....very stiff....I'm a really big guy and I have a hard time without em..

[Gomer Pylot]

With the hydraulics off, you don't fly it, you herd it. You don't even try to move the controls immediately, nor the full amount you need to move them. A little at a time will get it done, though. Let everything happen slowly - nothing should happen quickly, and never let things go too far in any direction. Your patience will be rewarded.

[PA Pilot]

With the hydraulics off, you don't fly it, you herd it. You don't even try to move the controls immediately, nor the full amount you need to move them. A little at a time will get it done, though. Let everything happen slowly - nothing should happen quickly, and never let things go too far in any direction. Your patience will be rewarded.

THanks, that strikes me, in my limited experience, to be true.

 

One of the things I was try to get at, though, is whether all helicopters have the same amount of apparent sloppiness/free play in the cyclic when the hydraulics are off. I also don't understand why there is free play, although I guess it's normal for an R44 because the POH mentions it.

[Gomer Pylot]

It's different for different models, because there are varying numbers of control tubes, bellcranks, etc in varying directions. It's direct mechanical coupling, and the amount of slop in each connection, and the number of connections, can vary widely. Take the time to do a detailed trace of the linkage from the head down to the controls sometime, at least those you can see, and a drawing for those you can't.

[PA Pilot]

It's different for different models, because there are varying numbers of control tubes, bellcranks, etc in varying directions. It's direct mechanical coupling, and the amount of slop in each connection, and the number of connections, can vary widely. Take the time to do a detailed trace of the linkage from the head down to the controls sometime, at least those you can see, and a drawing for those you can't.

I can understand that, but why does the slop go away when the hydraulics are on?

 

Sorry to belabor the question, but I'm really puzzled about this!

[Gomer Pylot]

With the hydraulics on, the servos are working, and you don't notice any slop.

[Guest pokey]

I highly doubt that it is "slop" in the rod-end bearings, as they are precision bearings & the inspection for looseness is verry verry small as far as radial & axial play is concerned.

 

The stick movement to get the swashplate to do the same thing w/or w/out the hydraulics, has to do w/ the geometry/assist of the servo placement,,,, ie:

 

with hydraulics, you move the stick a tiny bit & the servo moves the swashplate ALOT.

 

w/out, you move the stick a tiny bit & it doesnt allow the servo to "extend" so? the swashplate only moves a tiny bit too.

 

Papilot? do a ground check ( if it is allowed by the POH) ( hopefully you are allowed to do this w/ the engine running, but the blades NOT engaged--so you can physically watch the controls AND the swashplate) & see if this is the case,,, let me know as i am curious too----- i have some time working on & flying JetRangers, & as far as i can recall it went something like that.

 

I have never even been close to a 44 tho.

 

the idea behind servo assist is: you push a little--it pushes alot (w/hyd---your cyclic is actually connected to a valve in the servo that extends the piston) (w/out hyd--the servo acts like a "fixed dimension" linkage)

[PA Pilot]

That helps, Pokey, thanks. I don't think there's a way to do a ground check as you suggested -- the hydraulics pump is driven off of the top sheave, which means that the rotor clutch has to be engaged for it to work and the blades would then be turning, of course.

[Guest pokey]

yer welcom PaPilot, & if ya do fly that 44 over here for lunch? remember that restauant is closed on tuesday & wednesday

 

i suggested the ground check so you could "see" the difference,,,, ya can prolly try 1/2 of the check w/ engine off & see what i mean

[PA Pilot]

yer welcom PaPilot, & if ya do fly that 44 over here for lunch? remember that restauant is closed on tuesday & wednesday

 

i suggested the ground check so you could "see" the difference,,,, ya can prolly try 1/2 of the check w/ engine off & see what i mean

I love N40! I flew our R22 in there for one of those great burgers a month or so ago and then bopped over to Vansand for jollies.

[Goldy]

Squirrel - From what I've heard the squirrel becomes very hard to control. Some weaker people may not even be able to do it.

 

S76C+ - You've no chance! Impossible to move controls without it. Need hydraulics muchly! Also, if you lose hydraulics you may not be able to put gear down, unless you blow them down with emergency blowdown gas. Fortunately, there are 2 independent systems.

 

Joker

 

Joker- I was in a Sikorsky SkyCrane today, I asked the pilot what happened if you lost your primary and secondary hydraulics....he answered.." you die". Looking at the size of that rotor head, I believe him !

[blave]

I'm about done with my transition from the R22 to the R44. One of the things we worked on was run on landings with failed hydraulics.

 

Since my only experience with helicopters with hydraulic assisted controls is the R44, my question is:

 

When hydraulics are turned off in a hover, is the R44 typical of all helicopters in the amount of play (feels like a foot, but probably more like 1/2") in the cyclic? It struck me like trying to learn to hover all over again...

 

I cannot answer your question per se, but I wanted to mention that, during my last SFAR73 checkout, my (very capable) CFI said that in an R44 hydraulic failure situation, fly a running landing and don't try to do a pretty set-down - just run it on at speed and manage the slide-out. Based on what I experienced with that tiny toggle switch set to "off", I don't plan on any heroics in getting the ship on the ground in the event of a hydraulics failure.

 

Dave Blevins

[PA Pilot]

I cannot answer your question per se, but I wanted to mention that, during my last SFAR73 checkout, my (very capable) CFI said that in an R44 hydraulic failure situation, fly a running landing and don't try to do a pretty set-down - just run it on at speed and manage the slide-out. Based on what I experienced with that tiny toggle switch set to "off", I don't plan on any heroics in getting the ship on the ground in the event of a hydraulics failure.

 

Dave Blevins

The last couple of training sessions have been with the guy who did my PP-RH checkride. That's exactly what he said, and what he had me practice.

[Rob B]

The last couple of training sessions have been with the guy who did my PP-RH checkride. That's exactly what he said, and what he had me practice.

 

The "slop" noted is caused by the 'free-play' of the valving with in the servo with the hydr off - with the hyd on, the hyd pressure moves the controls as soon as the valve moves of seat.

hope this helps

[Autorotator]

That helps, Pokey, thanks. I don't think there's a way to do a ground check as you suggested -- the hydraulics pump is driven off of the top sheave, which means that the rotor clutch has to be engaged for it to work and the blades would then be turning, of course.

If I recall, the hydraulic pump is mechanically driven off of the main rotor gearbox (transmission). I just posted this in case someone investigating the hydraulic system on the R44 II doesn't get the wrong information.

[EAGLE1]

The EC120 is no problem to fly with the hydraulics off. It does take a bit more effort but it is completely controllable and the POH says a normal landing to a hover and set down. I have performed this maneuver numerous times during training without incident. The fenestron is not boosted so there is no trouble there.

[RockyMountainPilot]

The MD500 and MD600 series are real easy to fly without hydraulics:)

[darwin]

How heavy are the controls in an unboosted machine such as the md500 vs a boosted machine like a b206?

[RockyMountainPilot]

How heavy are the controls in an unboosted machine such as the md500 vs a boosted machine like a b206?

 

The controls are easier to move in a non-hydraulic machine than a hydraulic machine with the hydraulics off. This is because you are still moving the actuators as well which can require a great deal more force. The Astro and the Raven are perfect examples. The Astro is much easier to fly than the Raven with the hydraulics off.

[darwin]

The controls are easier to move in a non-hydraulic machine than a hydraulic machine with the hydraulics off. This is because you are still moving the actuators as well which can require a great deal more force. The Astro and the Raven are perfect examples. The Astro is much easier to fly than the Raven with the hydraulics off.

Undoubtedly. Just like an automobile. How would the required force between an MD500 (which does not have hydraulics, period) compare to something like

a b206 or r44 that does have hydraulics (assume the hydraulics are functioning normally)?

Does one tire after a while flying unboosted vs boosted, or is it just unnecessary on something like the 500?

 

Thanks,

-Darwin