SA-227, Reverse Question

[Hugh Johnson]

The fact you flew a Polish single engine crop duster begs stories at the bar. I googled the engine and came up with the Viking, Toscano, and the Predator Drone. I tossed the the drone out.

 

[avbug]

The Dromader isn't really the epitome of excitement in ag ops, but it certainly can be in other venues. I didn't spray with the dromader, but did fly one for seven years doing firefighting in the desert and in the mountains. (I sprayed with other aircraft...my first job out of high school was crop dusting).

During a steep, downhill run, airspeed control is a problem. Obviously airspeed wants to build, and during a drop the speed is an important consideration. This is particularly so in the Dromader, because per the BLM, it has a 15-20 knot drop speed window. Too slow and the airplane will stall during the drop as the retardant is released (and the drop door opened), and too fast will cause the airplane to pitch up vertically enough that no amount of forward stick or pilot input will prevent it. Both ways have caused a number of fatalities.

I didn't believe the reports I'd heard from another individual who'd been flying the Dromader in Canada. He'd seen a friend killed on a drop when the airplane pitched and couldn't be controlled, and stall-spun out of the pitch-up to an explosion near the drop site. My thinking at the time (this was many years ago) was that the fatality-pilot had simply failed to fly the airplane.

Fast forward years later on a very steep downhill drop in a canyon, and strong tailwinds, severe turbulence, and some nasty rotors on the downwind side of the ridge where I was dropping. The airplane in the shears would stall and buffet and then overspeed, and then stall again, on the baseleg to downwind final turns for the drop, and I was thumbing the flaps in and out for stall protection (and in to prevent overspeed). Airspeed control on a drop can be difficult, and under those conditions very difficult. I made seven runs into the target with some difficulty locating the specific spot in smoke, the steep terrain, and trees.

On the last run, with some frustration, I found the burning swail that a team of smoke jumpers wanted cooled with a shot of retardant, elected to go for it regardless of the speed, and punched off the load. The airplane pitched vertically and full forward stick had no effect. My chin was pushed down against my chest and as I picked my head up I saw the airspeed winding down to the bottom end. The only thought that popped into my head at the time was "Oh, so this is what XXX was talking about."

The event wouldn't have been survivable on level ground, but this was on a steep downhill run, with the terrain falling away to the east...and it enabled two thousand feet or so to recover. I used full rudder input and forward stick and sliced out of it in a poor upset-recovery, and headed for the tanker base. I was given a "load and return," but rejected the request at the time because I needed time to let my legs stop shaking.

That particular drop was in a Pratt-powered Dromader, using a PT6A-45R. The engine failure previously described took place in a Dromader powered with a TPE-331-10. (We were using -10's and -11's, midtime engine conversions from Jetstreams). The big advantage of the TPE-331 was the enormous drag rise, if the engine was set up for it, with the power retarded. I could do the same steep downhill runs with no airspeed increase...and even decrease airspeed. In fact, from level cruise, the power could be retarded to idle and the resulting performance loss was extremely dramatic. It would slow the airplane down fast enough to throw me forward against the shoulder straps, and require forward stick and a transition to the vertical to prevent a stall. The effect was very much like holding beta or reverse, rather than simply flight idle, and was due to the setup used in rigging the engine.

Obviously in that condition with a power loss or an inability to remove the airplane from that high drag condition would result in some real problems, particularly inside a narrow canyon with few options available, and that was the circumstance under which the previously described oil loss and failure occurred.

I also flew the Air Tractor AT502 and AT802 on fires, and these lack the high drag capabilities of the Garrett motor...they build up speed easily, and require a lot more forethought and planning in not only a drop run but an exit. They've also got considerably more performance than the Dromader, though at the cost of being a lot more sensitive and potentially demanding, too. Nice flying airplanes, any of them will easily eat one's lunch at any time, if allowed. There are always tradeoffs, and that's the cost of performace in the case of those airplanes. Considering their capabilities and utilities, it's a good tradeoff.

 

[Guitar rocker]

I used to fly an SA-227 quite a few years ago. The particular operator who I was flying for had filed chapter 11, moved their mx base and as a result many of the experienced mechanics didnt want to move (and thus resigned) and then they hired kids right out of maintenance school (cheaper cost). The pressure was on to get those birds out of the hangar and make some revenue! It was always a bit scary when picking one up out of maintenance though. Anyway, here we are cleared for takeoff, bring the speeds high and looking for the 97%....except all we had was about 95.5 to 96% on both engines. We brought the speeds back to low and tried again and only got 95% on both engines this time. Even checked the friction lock to make sure the speeds were not creeping back. Couldnt make sense of that and decided to bring er back and shut er down....with plenty of resistance from our mx friends and the company ofcourse. After deplaning everyone, my FO comes back has me look up into the wheel well on the RH engine. Sitting way up inside the wheel well was a large tool with a pressure guage that one of the mechanics forgot to take out.....I was told the tool was hooked to some bleed lines which resulted in the less than 97% min for speeds high. FO preflight could have been a bit more thorough especially coming out of mx with this particular commuter. Regardless, I had just never seen anything like that before. Thought that Id pass it on.

 

[CaptSeth]

......Sitting way up inside the wheel well was a large tool ......

I love it when you talk that way. You got a purdy mouth, boy...

 

[Guitar rocker]

I love it when you talk that way. You got a purdy mouth, boy...

Heeellloooo poooolllle. HA. Ahhh, it was "way up there." I cant blame the other guy, I would have missed it myself too.

 

[Checks]

There is a mechanical connection between the power levers whenin reverse and the underspeed governor. When the power levers go into reverese they mechanically reset the USG higher, up to @80%.