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Pilot Report: Sopwith Camel

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Wanttaja

Sky Savant
Joined
Sep 15, 2013
Messages
2,854
Location
Seattle, WA
A couple of years back, I attended a seminar at Seattle's Museum of Flight on aviation in the Great War. One of the speakers was Mr. Javier Arango, who owns what is probably the largest collection of WWI airplanes in the world...and I'm NOT excluding museums! He owns something like two dozen WWI airplanes.

Arango-Triplane-7-520.jpg

They're all replicas, but Mr. Arango has gone through considerable effort to make them *accurate* ones. Most are the right size, have original airfoils, the same weight. And more important, most have *the original engines*.

One such example is his Sopwith Camel...powered by a 160 HP LeRhone rotary. Full scale, original airfoil, original loading. The following is taken from a Facebook posting I made the day of the event.

Now, the Camel has a bad reputation today as a pilot-killer. Deservedly so, really... about the same number of Camels and SE-5s were built (5500 vs. 5300) but the Camel had a fatality rate in training *over four times higher* (~450 fatalities vs. 80).

There are plenty of rumors about the handling problems of the plane... but these are colored by a 100 years of fading history and the alteration of the English language itself. A pilot writing in 1918 about "roll rate" was not necessarily referring to the same term as used by a 21st-century Pitts pilot.

Mr. Arango was curious. He also had a Sopwith Camel that was, for all intents and purposes, what they flew in 1917. And, of course, he had access to the technological wonders of the current age.

The solution was straightfoward: Instrument his Camel like a modern flight test aircraft, and perform a set of formal tests.

That's what his talk was about today. The plane was loaded with accelerometers, sensors, and recorders, and he showed the aircraft's behavior and performance.

The key points in his presentation addressed the rumors about the Camel... "Turns to the right three times faster than to the left." "Would fly sideways if you're not careful." "Would drop into a spin and kill fledgeling pilots at the drop of a hat."

What'd he find?

First, the Camel was not stable. He showed a plot of a pitch phugoid test... fly level, haul the nose up 15 degrees, then release the stick. A modern airplane will pitch down, speed up, nose up, pitch down at a gentler angle, then pitch up slightly, until the pitch deviation is damped out and the plane is flying at its trim speed.

The Camel? Pitch up to ten degrees, release the stick. Nose drops ~2 degrees, then pitches up to 15 degrees. Hesitates a second or so, then heads up to 25 degrees pitch-up....at which point Mr. Arango takes over ("Chickens out", as he put it). Roll and yaw stability were neutral to divergent.

Then again... the Camel *is* a fighter. It's not supposed to be stable. A lot of WWI airplanes share those characteristics.

Verifying the turning issues was the fascinating part. Mr. Arango got the Camel stabilized in level flight, then moved the stick to the left with no rudder or pitch input.

The plane banked left, but the nose went hard right! It has massive adverse yaw. Mr. Arango showed a side-on view of an aileron. It was hinged on the *bottom* of the wing... so when the aileron went down, a large gap yawned wider on the upgoing wing, massively creating additional drag which yawed the plane opposite to the desired direction.

Then again... most airplanes of this era showed adverse yaw. Every Sopwith prior to the Camel had its ailerons hinged on the bottom as well. And every Sopwith AFTER the Camel moved the hinge up. (And, of course, the Fly Baby puts the aileron hinge on the TOP.)

In a second test, Mr. Arango stabilized the airplane in level flight. He held the stick steady, and pressed the left rudder. The plane entered a normal, classic, coordinated turn. Same to the right.

However, there was another factor: In the left turns, the nose would rise about 20 degrees, and in the right turns, the nose would fall about 20 degrees. Gyroscopic precession.

And...this is where it got ugly.

Say you're a neophyte Camel pilot, and you press the right rudder to start a turn to the right (you've got to lead with the rudder due to the massive adverse yaw). The nose drops suddenly, and your instinct is to pull back on the stick to lift it. But this only aggravates the gyroscopic precession...and the nose drops further. Panicking, the youngster pulls back harder...and the problem just gets worse and worse until he's in a tight spiral towards the ground.

Camel pilots had to learn to correct the rise/fall of the nose in turns *using the rudder*. If the nose is dropping to the right, pick it up with left rudder.
But...it bit often enough. New Camel pilots were told not to try a right-hand turn below 1,000 feet until they had a hundred flight hours.

Then again, LOTS of WWI airplanes had the same sorts of engines...and the same sort of behavior. Mr. Arango showed us a picture of the instrument panel of his Avro 504K trainer, with an 80-HP rotary. The panel included a placard on how to turn to the left ("Move rudder and warp controls to the left simultaneously...center the rudder, move warp controls slightly right....Press right rudder and right warp control simultaneously to level wings."

There ISN'T a similar placard for right turns. Because the students weren't supposed to do them without an instructor.

Why was the Camel different? Probably because it had all the weight concentrated, a short tail, and a much larger rotary engine (160 HP) than the norm.

Once pilots learned to handle this...they loved the airplane. It maneuvered extremely quickly. The maneuver that killed Camel students actually *saved* experience pilots in combat. No German plane could stick with a Camel in that plunging hell-spiral, and an experienced pilot could recover with ease.

Arango tested the Camel's turn normal rate in both directions: In both left and right turns, a complete 360 was completed in the same time. The Camel DIDN'T have a faster turn rate to the right, like "common wisdom" says today.

But... when the chips were down, a Camel pilot could turn hard right, suck the stick back, and wave bye-bye as the plane spiraled down in a blur. And THAT'S how the Camel got its reputation for being able to out-turn German aircraft towards the right.

Fascinating program....

Ron Wanttaja
 
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