Wheel Landings 170

blueldr · Post by **blueldr** » Sun Nov 01, 2015 6:14 pm

48rwflyboy,

Have you ever actually weighed your tail wheel? 200 pounds sounds like a lot of weight to me. I don't remember what my '52 B model used to weigh, but I'm sure it was considerably less than that or Iwouldn't have been able to lift it for maintenance.

48rwflyboy · Post by **48rwflyboy** » Sun Nov 01, 2015 7:03 pm

I think we did measure it but a long while back. When loaded down in the rear seat or hauling my camping gear to Oshkosh, it certainly is real heavy on the tail. I will take my bathroom scales with me next trip to the hangar. I cannot lift the tail even with another old timer like me but have a jack that does it well. Stay tuned!

Post by **GAHorn** » Mon Nov 02, 2015 12:03 pm

48rwflyboy wrote:...The most interesting thing I have realized is how much using flaps even in strong x-wind conditions helps keep the center of pressure further aft of the CG helping directional stability and rolling out tail high to pin it onto the runway. If your rear seat is occupied, this really helps balance out the rearward CG. Of course braking is necessary to get down below stall speed before lowering the tail. If you have any doubt about the effectiveness of how the moving the center of pressure back helps, just land with flaps and try retracting them during the roll out! I used to think that would help pin it onto the runway but it actually caused a severe drop in the tail and a struggle to keep things straight. Not to mention taking your hand off the throttle for a second or two is a bad idea. Would love to fly an A or B model sometime to see any difference those flaps might make.

Huh?
... "center of pressure"..?? "aft of the CG"..??
"rear seat occupied...helps... rearward CG"...??
"raising flaps... drop..the tail..." moves the "center of pressure back.."...???

I'm not following what you mean by "center of pressure". And if your rear seat is occupied... that would move your "rearward" CG further aft, so how could it help "balance it out"?

The "drop" of the tail when retracting the flaps has nothing to do with any "center of pressure" that I can understand. Application of flaps moves the center of LIFT aft along the wing chord. This places the center of LIFT (C/L) further aft of the forward CG.... and helps explain why retraction of flaps (which moves the C/L further forward... might add impetus for the tail to move down and stay there (since it's no longer being assisted by the previous aft C/L.)

In airplanes that are considered "longitudinally stable", the CG will be forward of the C/L. Any movement aft of that C/L will place an increased burden of "downward lift" upon the empennage (because the horiz/stab/elevator provide downward lift to oppose the forward CG which is forward of the C/L. I.E., the fuselage is a "lever", the C/L is a "fulcrum" and the tail holds the forward CG/Nose UP using downward force.
Lowering flap shifts the C/L aft, thereby creating a greater workload for the tail. This is counteracted in high-wing airplanes by the downwash of relative wind in front of the horz/stab thereby increasing it's AOA. This may be perceived by the pilot as a pitch-change because the combination of change is C/L and empennage workload. Reduction of speed will reduce lift and tail AOA and return the airplane to it's previously-trimmed state (which is why it's unnecessary to constantly apply flaps, retrim, slow down, retrim, more flaps, retrim... etc etc.

If from a cruise one were to reduce power to approach power (say, 1500-1700 RPM) and as the airplane slows and gets "nose heavy"... if one applies flaps, the airplane will return to a previously-trimmed state without changing trim at all.

After landing, removing flaps dumps lift and helps settle the tail.

I'm writing this at 6AM when I've been up all night so hope it still makes sense tomorrow.

48rwflyboy · Post by **48rwflyboy** » Mon Nov 02, 2015 5:39 pm

"gahorn wrote:

The "drop" of the tail when retracting the flaps has nothing to do with any "center of pressure" that I can understand. Application of flaps moves the center of LIFT aft along the wing chord. This places the center of LIFT (C/L) further aft of the forward CG.... and helps explain why retraction of flaps (which moves the C/L further forward... might add impetus for the tail to move down and stay there (since it's no longer being assisted by the previous aft C/L.)

I think we are on the same page George but we are in different airplanes with our experiences (Ragwing vs. A & B models).........The terms Center of Pressure and Center of Lift or even Aerodynamic Center I think all mean the same thing and it must never be forward of the CG or you will be in trouble. I have never flown an A or B model with the barn door flaps but have flown Cessna 150's which always seem to pitch up (opposite of my Ragwing) on application of flaps where the down-wash on the elevator was a bigger pitch factor than the CL or CP moving aft. My Ragwing 170 always lifts the tail and pitch goes nose down when flaps are applied for landing on the mains. Probably due to the very little effect from down-wash with the smaller flaps. I was pointing out that the lowered flaps on the Ragwing moved the lift further back of the CG in a wheel landing which was similar to helping pick up the tail weight (especially helpful with extra loads in the rear). I have to use far less forward yoke pressure to keep her on the mains and it feels more stable rolling out. Years ago in my first experiments in trying to pin it to the runway, I would retract the flaps while the tail was still high and my speed still above stall in a x-wind but that caused a sudden drop of the tail before I could react to the change which often sent me in wrong directions. Over time it was apparent that leaving the flaps down on the roll-out was the better approach. I assumed the same thing would be true in other 170's but it may be just the opposite in an A or B model in the same landing configuration when flaps are retracted on roll-out. Hope I didn't cause any loss of sleep! Great discussion.

Ernie

48rwflyboy · Post by **48rwflyboy** » Sun Nov 08, 2015 5:52 pm

Re: Wheel Landings 170
by blueldr » Sun Nov 01, 2015 1:14 pm

48rwflyboy,

Have you ever actually weighed your tail wheel? 200 pounds sounds like a lot of weight to me. I don't remember what my '52 B model used to weigh, but I'm sure it was considerably less than that or Iwouldn't have been able to lift it for maintenance.

Just weighed it today in the hangar with full fuel (50 gal) and is was exactly 200 lbs. With pilot and co-pilot, probably would weigh much more. Just to let you know that several years (many years), I did lift it for maintenance, but me and my 170 have aged and what I use-to-could, I cannot anymore!

48rwflyboy · Post by **48rwflyboy** » Sun Nov 08, 2015 6:19 pm

No, just sitting as in "3-point landing configuration".

blueldr · Post by **blueldr** » Mon Nov 09, 2015 6:12 pm

200 pounds still sounds pretty heavy to me. I have had to change a tailwheel tire up at Johnson Creek and I don't seem to remember the tailwheel being anywhere near that heavy. I do remember lifting it with my back under the horizontal stabilizer.

48rwflyboy · Post by **48rwflyboy** » Mon Nov 09, 2015 6:59 pm

Blueldr wrote:

200 pounds still sounds pretty heavy to me. I have had to change a tailwheel tire up at Johnson Creek and I don't seem to remember the tailwheel being anywhere near that heavy. I do remember lifting it with my back under the horizontal stabilizer.

Also did the same lifting with the back many years ago. Can't do that anymore at my age without doing harm! Anyway, the conversation about wheel landing vs. 3-pointing with lots of weight back there on the little wheel makes me prefer the wheelee. That's the only reason for bringing up the weight. Used to fly a Taylorcraft and it was so light in the back I could lift it with one hand. Almost always 3-pointed it too.

Saw the wing cam videos Aryana posted landing and if everyone landed as smoothly as he does, the tail wheel would last forever! Fantastic videos from many different views......pretty 170B!
http://s8.photobucket.com/user/aaryana/ ... s.mp4.html

48rwflyboy · Post by **48rwflyboy** » Mon Nov 09, 2015 7:30 pm

I love the videos you posted and just saw the short field which is amazing! Never saw a 170 do that before! Are you using a Go-Pro?

jmurtap · Post by **jmurtap** » Tue Nov 10, 2015 1:49 am

I'm still a relativity new driver with around 75hrs in the 170. I still have bounces on both 3 point and wheelies occasionally, especially when I'm trying to hit a spot. Occasionally everything comes together just right. My best landing (shortest) to date just happened to get caught on film. https://www.facebook.com/jpatrum/videos ... 9885385526 Anymore I rarely try to hold a 3 point after touchdown unless field conditions warrant it. Nothing really compares to a long wheel landing you cant even feel (or hear) the touchdown. At my skill level this require much more runway however..lol

johneeb · Post by **johneeb** » Tue Nov 10, 2015 2:20 am

Jason, did you drive for nascar before you took up flying? (victory celebration donuts)

cessna170bdriver · Post by **cessna170bdriver** » Tue Nov 10, 2015 3:09 am

blueldr wrote:200 pounds still sounds pretty heavy to me. I have had to change a tailwheel tire up at Johnson Creek and I don't seem to remember the tailwheel being anywhere near that heavy. I do remember lifting it with my back under the horizontal stabilizer.

200 lbs. doesn't sound out of the realm of possibility to me. I used to lift mine that way too, and I always noticed that it got MUCH lighter as it raised.

PS: After seeing my buckled left side horizontal stabilizer ribs a few weeks ago, I vow to never lift it that way again.

blueldr · Post by **blueldr** » Tue Nov 10, 2015 3:59 am

Miles,

When it becomes necessary to lift the tail of an airplane in, or on, a back country air strip, one uses what is available.

48rwflyboy · Post by **48rwflyboy** » Tue Nov 10, 2015 10:59 am

Oh my! When blueldr said he lifted it with his back, and I did the same thing, I never pictured lifting from the horizontal stabilizer, but only from under the fuselage itself very near the tail getting down on all fours and lifting only with my back long enough to let someone put a block of wood under the tailspring. Sorry to here about the buckled ribs! Did I read your post right cessna170driver?

edbooth · Post by **edbooth** » Tue Nov 10, 2015 5:39 pm

blueldr wrote:Miles,

When it becomes necessary to lift the tail of an airplane in, or on, a back country air strip, one uses what is available.

I have lifted mine a couple times having to repair a flat tail wheel tire down at the end of a long runway. I always lifted the tail making sure I was directly under the horizontal stabilizer spar, close to the fuselage. I always carried a spare tire/tube, tube repair kit and a small air pump just in case.