C172RG fire

[wsuffa]

There's not really any benefit to using hydraulics vs. an electric design, especially since the hydraulic pump is electrically driven. The safety record concerns me as well.

As with anything, you pays your money and you takes your chances.

The key difference depends on execution.

On the Pipers and Commanders, the hydraulic system is used to cycle the gear and hold the gear up. Loss of hydraulic pressure causes the gear to drop. That means that a loss of electrical power will still allow you to drop gear by using the hydraulic dump valve.

It's different from the Cessna design.

 

[Fearless Tower]

On the Pipers and Commanders, the hydraulic system is used to cycle the gear and hold the gear up. Loss of hydraulic pressure causes the gear to drop. That means that a loss of electrical power will still allow you to drop gear by using the hydraulic dump valve.

Except for the Comanches - all electric gear - no hydraulics

 

[bnt83]

Except for the Comanches - all electric gear - no hydraulics

And a big rubber band (and gravity) pulls the gear down after a bang! from the transmission disconnect :wink2:

 

[Ted]

The key difference depends on execution.

On the Pipers and Commanders, the hydraulic system is used to cycle the gear and hold the gear up. Loss of hydraulic pressure causes the gear to drop. That means that a loss of electrical power will still allow you to drop gear by using the hydraulic dump valve.

It's different from the Cessna design.

That's been my point as well.

The other key feature of the Piper and Commander hydraulics is I don't see them have failure modes known for spraying hot hydraulic fluid in the cabin. The Aztec's system is particularly good - if you can't get the gear down on it, there's probably a major structural issue.

 

[spinfire]

The Cardinal RG gear is subject to one limitation which I believe is common to all high wing Cessna retracts. This limitation is that it is not possible to get the gear down if sufficient hydraulic fluid has been lost. Several Cardinal Flyers Online members have made a modification that adds a "gear pump running light". If the gear pump starts running frequently in flight then there is a leak (the pump is actuated solely by pressure and squat switch in most if not all Cardinal RGs). So if the light comes on for more than a quick blip with the gear not in transit then GET IT DOWN NOW before the hydraulic fluid is gone. I have had a problem with the gear pump running in small blips more frequently than it should have been but it was just old seals in the actuators leaking down internally. I saw the blip on my ammeter but the gear pump running light would have made it more obvious.

In all Cardinal RGs the hydraulic power pack is in the tailcone, next to the battery. The power pack also includes the reservoir and you fill it from there. This seems to avoid the fire issue and Cardinals are not subject to this fire SB/AD. In a pinch after a leak you could empty some fluid into the reservoir if you have someone small to crawl in the baggage area... supposedly it has been done. Better to get the gear down immediately and keep it down until you are on the ground if you ever suspect a leak.

The biggest problem with the gear in the Cardinal is Cessna was evolving the design a lot. By '76 most of the kinks were worked out and the design is simpler. All are reasonable designs but because there are differences between each year you'd best be sure your A&P/IA knows the details. CFO has a great breakdown of the differences.

 

[Ted]

Good info on the Cardinal, sounds like they improved the safety asppects of the design by then.

 

[spinfire]

Though the Cutlass (172RG) came after the Cardinal so I'm not sure what's up with that.

 

[tonycondon]

Though the Cutlass (172RG) came after the Cardinal so I'm not sure what's up with that.

The cardinal has cantilevered wing so there isn't as much room above for your head so they move the floor down. now there isn't room in the floor for the hydraulic power pack so they put it in the tail. maybe they had a tendency to go nose heavy anyway so the weight in the tail helped with that too.

The 172RG has a strut braced wing so you can fit your head up between the wings, the area between the floor and the bottom of the plane can be larger, and there is room for the hydraulic power pack, nice and close to the gear it is operating.

 

[spinfire]

The Cardinal RG can be nose heavy. The battery is back in the tailcone with the power pack as well. I'm not particularly heavy and I have had situations where someone over 200 pounds is in the right seat and some weight is needed in the baggage area or rear seat to keep the CG within limits. It is much easier to hit the forward CG limit in a Cardinal RG versus a 172 or 182. I think this is because of the placement of the wing.

In any case, the Cardinal's gear is not subject to this AD, so apparently they did something right.

 

[tonycondon]

Yea, wing further back so the spar doesn't interfere with head space, forward cg becomes an issue.

i just love the trickle down effect of airplane design choices. how one change will drive another that on the surface have absolutely nothing to do with each other.

 

[Fearless Tower]

The Cardinal RG gear is subject to one limitation which I believe is common to all high wing Cessna retracts. This limitation is that it is not possible to get the gear down if sufficient hydraulic fluid has been lost. Several Cardinal Flyers Online members have made a modification that adds a "gear pump running light". If the gear pump starts running frequently in flight then there is a leak (the pump is actuated solely by pressure and squat switch in most if not all Cardinal RGs). So if the light comes on for more than a quick blip with the gear not in transit then GET IT DOWN NOW before the hydraulic fluid is gone. I have had a problem with the gear pump running in small blips more frequently than it should have been but it was just old seals in the actuators leaking down internally. I saw the blip on my ammeter but the gear pump running light would have made it more obvious.

In addition to the light, I have also talked to a couple Cardinal owners who installed a separate backup hydraulic reservoir for emergency use.



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[bnt83]

In addition to the light, I have also talked to a couple Cardinal owners who installed a separate backup hydraulic reservoir for emergency use.



Sent from my iPad using Tapatalk HD

In addition to that, those darned nose gear uplocks on them have caused many hangups.. Some have a manual cable operated uplock release. I think Austrailia required them.

 

[Ghery]

After flying a Cardinal I find that C172/182 airplanes make me feel like I'm in a nuclear submarine.

But a nuclear submarine has a lot more power and you can walk around in one.

No uplocks on Pipers. the Hyd. system has to hold, or the pump runs again. That's why "gravity" drop usually works.

The key difference depends on execution.

On the Pipers and Commanders, the hydraulic system is used to cycle the gear and hold the gear up. Loss of hydraulic pressure causes the gear to drop. That means that a loss of electrical power will still allow you to drop gear by using the hydraulic dump valve.

It's different from the Cessna design.

True. All my retract time is in an Arrow, and the emergency extension system works great.