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Piper's Beloved Stabilator  
User currently offlineJzucker From United States of America, joined Nov 1999, 100 posts, RR: 0
Posted (13 years 11 months 3 weeks 4 days 23 hours ago) and read 6796 times:

Hi All...

Just wondering the aerodynamic advantages to the Stabilator the Piper uses on all of its light aircraft. Their engineers must have a reason to choose it over the conventional elevator. I assumer the stab. is more complex, as it requires an anti servo tab to provide control feel.

Thanks a lot!

6 replies: All unread, jump to last
User currently offlineDufo From Slovenia, joined May 1999, 846 posts, RR: 4
Reply 1, posted (13 years 11 months 3 weeks 4 days 23 hours ago) and read 6794 times:

The piper selection of the stabilator instead of the conventional stabilizer/elevator configuration was done for several reasons. The stabilator gives a wider range of pitch control over all flight speeds. The stabilator is lighter with lower drag. The use of the anti-servo trim design causes the tab to move with the stabilator but the combination requires more pilot input with any increase in speed or deflection. . The stabilator utilizes an "antiservo" tab that deflects upward on the trailing edge of the stabilator as the controls come back. This antiservo tab generates the necessary control feel and feedback to the pilot to maintain the necessary "stick force per G" to keep a hamfisted pilot from easily breaking the airplane with excessive control movement. This is a safety device improves longitudinal stability while at the same time limiting the pilot ability to cause structural damage.

The "stabilator" affects flight exactly the same as an elevator. However, stability is more difficult to attain with the stabilator because its larger effective surface increases sensitivity. There are two different sizes of stabilators on PA 28 aircraft. One is over three feet less than the other. The control effectiveness of these in landings makes it very important that the pilot be aware of which stabilator is on the aircraft. There are distinctive skills required for proper flying of the older Hershey bar wing with the small stabilator. The older (smaller) stabilator will run out of effectiveness at slower speeds. This is especially critical when the aircraft is loaded toward the aft limits. The stall under these conditions will be unlike any usual Piper stall. It will be abrupt, violent and give a spin all in the same moment. Fuel consumption will cause a gradual rearward movement in the weight and balance envelope. Pipers at gross tend to fly tail low with much greater fuel consumption.

(from www.whittsflying.com)


I seriously think I just creamed my pants without any influence from any outside variables.
User currently offlineJETPILOT From United States of America, joined May 1999, 3130 posts, RR: 27
Reply 2, posted (13 years 11 months 3 weeks 4 days 22 hours ago) and read 6777 times:

Locheed thought a stabilator was such a good idea they put it on the L1011.


User currently offlineDL_Mech From United States of America, joined Feb 2000, 2290 posts, RR: 9
Reply 3, posted (13 years 11 months 3 weeks 4 days 21 hours ago) and read 6770 times:

And Cessna on the C-177 Cardinal........

This plane is built to withstand anything... except a bad pilot.
User currently offlineJetguy From , joined Dec 1969, posts, RR:
Reply 4, posted (13 years 11 months 3 weeks 4 days 20 hours ago) and read 6762 times:

But don't forget the original Cardinal stabilator was a disaster. Cessna had to recall the entire production up to that date and install slots in the leading edge. I flew an early one w/o the slots for a little while. It could get real nasty.


User currently offlineJETPILOT From United States of America, joined May 1999, 3130 posts, RR: 27
Reply 5, posted (13 years 11 months 3 weeks 4 days 15 hours ago) and read 6743 times:

Nasty? How so?


User currently offlineJetguy From , joined Dec 1969, posts, RR:
Reply 6, posted (13 years 11 months 3 weeks 4 days 6 hours ago) and read 6718 times:

I had the opportunity to fly one of the very first C177s back when they first came out. At the time, I had about 200 hours, most of it in Champs and Cessna 170s. It was a real hand full. The Cardinal was introduced back in 1968 as the 172 Skyhawk replacement. The first year they built nearly 1,200 airplanes! The original airplanes had several problems:

1. They were under powered - it had only 150 HP. Additionally it had 50 pounds less useful load and bigger fuel tanks than a C172, so it was very easy to overload.

2. The originally, the C177 had the "high performance" NACA 6400 series airfoil - the same one used on the Learjet. It's a great airfoil on the Lear, but it tends to build up drag quickly at high angle of attack and low airspeeds - not a particularly good trait for an airplane flown by low-time, step-up pilots. Additionally, the stall speed was higher than the Skyhawk's. The stall and rate of climb "book numbers" don't look too bad, but they were pretty "optimistic" - a common problem with light aircraft performance data from that era. In the real world, the airplane climbed very poorly under the best of conditions, and if the pilot got the nose up a little too high, the drag built up quickly and the climb rate sagged even more.

3. The "final straw" so to say, was the fact that the airplane was very sensitive on the controls - particularly in pitch. The stabilator had a tendency to stall in the landing flare, resulting in a sudden loss of tailpower which dropped the nosewheel onto the runway. Porpoising,wheel-barrowing, and bounced landings, and the damage they cause, were very common.

Overall, because of its tricky landing traits, overloading tendency, and doggy climb performance made it a real handful for the typical Skyhawk pilot.

To fix the problems, in 1969, Cessna recalled all of the 1968 C177s and modified the stabilator by adding slots to the leading edge. This cured the pitch and porpoising problem. In 1969 Cessna changed the designation to the C177A. This airplane had the stabilator slots and a 180 HP Lycoming. Additionally, there were a couple of aircraft modifiers who made a pretty good living retrofitting 180 HP engines into the 150 HP airplanes. In 1970, Cessna came out with the C177B. This was a 180 HP airplane, with a slotted stabilator and a new wing. The new airfoil was a NACA series 2400 similar to the Skyhawk's.

I've got quite a bit of time in the newer "B" airplanes (and the "RG" model too). The mods really made a difference and the newer airplane are very nice to fly. I hope this answers your questions.


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