T-tailed Bush Plane
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T-tailed Bush Plane
Need some technical assistance of an aerodynamic nature? I've been pondering a few issues regarding bush planes specifically those designed for exceptional STOL performance. Watching videos of the Valdez STOL competition virtually all the planes apply and hold brakes while using propwash to lift the tail prior to take off. While this makes perfect sense with a low mounted horizontal stabilizer would the same propwash lift a t-tail plane's "rear-end"? I understand the propwash lifting effect of a tail within the same or near to horizontal axis with a T-tail configuration however the horizontal stabilizer is now above that axis, so would the propwash still lift the tail with the same authority? Thanks!
I guess I'm not seeing why it should matter, unless the T-tail is high enough to be outside the prop wash. If anything, I'd expect the higher tail to have a slightly higher AOA, assuming the air travels from the prop to tail in a straight line. Also, depending on the height of the propeller, the thrust acting against the locked wheels would create a pretty good nose-down moment even without any lift from the tail.
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@Chu Chu, thank you for your input. My research on the subject leads me to believe it is somewhat important being able to get the tail "up" on a short airstrip a term loosely used in the bush...
While it will depend on the exact aircraft type, especially prop radius vs. VS length, a T-tail is generally NOT in the propwash at all, and will behave differently. The propwash is a "tube" the same radius as the prop, and will pass right under the HS.
I got my ticket in a Beech Skipper (T-tail similar to the Piper Traumahawk).
It had noticeably different short/soft-field behavior than low-tail Cessnas/Warriors. Holding the stick back at the start of the roll did nothing at all to raise the nose until about 30 knots IAS - at which point the airspeed (not the propwash) kicked in very suddenly to lower the tail, raise the nose and lift off into ground effect.
With the T-tail, I was trained to be ready to release back-pressure right now once the elevators kicked in, to keep from climbing right out of ground effect and getting a down-check on that portion of the checkride.
And in fact I was warned not to ever take the Skipper onto actual soft-fields, because the T-tail just couldn't protect the nose-wheel as well as low-stabilizer aircraft. T.O. or landing, it was not possible to hold the nose up out of the grass/mud at low airspeeds, due to the lack of propwash over the HS.
Now that is, of course, backwards to raising the tail of a tail-dragger, but it clearly indicated to me that T-tails just don't follow the same rules when it comes to STOL elevator techniques.
Except for a couple of motor-gliders (Dimona and Grob) is there even such a thing as a T-Tail taildragger?
I got my ticket in a Beech Skipper (T-tail similar to the Piper Traumahawk).
It had noticeably different short/soft-field behavior than low-tail Cessnas/Warriors. Holding the stick back at the start of the roll did nothing at all to raise the nose until about 30 knots IAS - at which point the airspeed (not the propwash) kicked in very suddenly to lower the tail, raise the nose and lift off into ground effect.
With the T-tail, I was trained to be ready to release back-pressure right now once the elevators kicked in, to keep from climbing right out of ground effect and getting a down-check on that portion of the checkride.
And in fact I was warned not to ever take the Skipper onto actual soft-fields, because the T-tail just couldn't protect the nose-wheel as well as low-stabilizer aircraft. T.O. or landing, it was not possible to hold the nose up out of the grass/mud at low airspeeds, due to the lack of propwash over the HS.
Now that is, of course, backwards to raising the tail of a tail-dragger, but it clearly indicated to me that T-tails just don't follow the same rules when it comes to STOL elevator techniques.
Except for a couple of motor-gliders (Dimona and Grob) is there even such a thing as a T-Tail taildragger?
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Thanks Pattern,
Your post was more the experienced based feedback I was looking for and yes there is at least one T-tail taildragger that I know of, the Pipistrel Virus SW also available in tricycle configuration. I had been focussed on the Virus until further research indicated that while you could mount tundra tires it was never designed as a BCP. I figured there might be little chance of a t-tail being "lifted" by propwash but I needed confirmation. My next question would be -I may just need to start a new thread- how about a V-tail being lifted by propwash?
Your post was more the experienced based feedback I was looking for and yes there is at least one T-tail taildragger that I know of, the Pipistrel Virus SW also available in tricycle configuration. I had been focussed on the Virus until further research indicated that while you could mount tundra tires it was never designed as a BCP. I figured there might be little chance of a t-tail being "lifted" by propwash but I needed confirmation. My next question would be -I may just need to start a new thread- how about a V-tail being lifted by propwash?
While it will depend on the exact aircraft type, especially prop radius vs. VS length, a T-tail is generally NOT in the propwash at all, and will behave differently. The propwash is a "tube" the same radius as the prop, and will pass right under the HS.
I got my ticket in a Beech Skipper (T-tail similar to the Piper Traumahawk).
It had noticeably different short/soft-field behavior than low-tail Cessnas/Warriors. Holding the stick back at the start of the roll did nothing at all to raise the nose until about 30 knots IAS - at which point the airspeed (not the propwash) kicked in very suddenly to lower the tail, raise the nose and lift off into ground effect.
With the T-tail, I was trained to be ready to release back-pressure right now once the elevators kicked in, to keep from climbing right out of ground effect and getting a down-check on that portion of the checkride.
And in fact I was warned not to ever take the Skipper onto actual soft-fields, because the T-tail just couldn't protect the nose-wheel as well as low-stabilizer aircraft. T.O. or landing, it was not possible to hold the nose up out of the grass/mud at low airspeeds, due to the lack of propwash over the HS.
Now that is, of course, backwards to raising the tail of a tail-dragger, but it clearly indicated to me that T-tails just don't follow the same rules when it comes to STOL elevator techniques.
Except for a couple of motor-gliders (Dimona and Grob) is there even such a thing as a T-Tail taildragger?
I got my ticket in a Beech Skipper (T-tail similar to the Piper Traumahawk).
It had noticeably different short/soft-field behavior than low-tail Cessnas/Warriors. Holding the stick back at the start of the roll did nothing at all to raise the nose until about 30 knots IAS - at which point the airspeed (not the propwash) kicked in very suddenly to lower the tail, raise the nose and lift off into ground effect.
With the T-tail, I was trained to be ready to release back-pressure right now once the elevators kicked in, to keep from climbing right out of ground effect and getting a down-check on that portion of the checkride.
And in fact I was warned not to ever take the Skipper onto actual soft-fields, because the T-tail just couldn't protect the nose-wheel as well as low-stabilizer aircraft. T.O. or landing, it was not possible to hold the nose up out of the grass/mud at low airspeeds, due to the lack of propwash over the HS.
Now that is, of course, backwards to raising the tail of a tail-dragger, but it clearly indicated to me that T-tails just don't follow the same rules when it comes to STOL elevator techniques.
Except for a couple of motor-gliders (Dimona and Grob) is there even such a thing as a T-Tail taildragger?
I can certainly attest that this effect works significantly in landings as well. I did my initial training in a Diamond DA20, which is a very clean bit of kit and reluctant to slow down. It has a T tail. So I got into the habit of closing the throttle ‘over the fence’ to ensure we didn’t go too deep. Very little trim change was involved.
Come the day I went to get checked out in a PA28. All went well and the instructor was convinced I could fly, till on final I whacked the throttle closed! Felt like we had been shot down; and suddenly the windscreen was full of grass and runway. The actual touchdown was actually ok, but the instructor had been caught off guard and was not happy.
So yes, T tails give very different handling power in Vs power off.
Come the day I went to get checked out in a PA28. All went well and the instructor was convinced I could fly, till on final I whacked the throttle closed! Felt like we had been shot down; and suddenly the windscreen was full of grass and runway. The actual touchdown was actually ok, but the instructor had been caught off guard and was not happy.
So yes, T tails give very different handling power in Vs power off.
