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| Floats always add sex appeal to land planes, don't they? photo courtesy Tecnam |
Dubbed the P92 Sea-Sky Hydroplane, this waterbird should prove to be yet another fun entry into the SLSA sweepstakes.
My impression of the Eaglet remains: a lively, forgiving, fun-to-fly all metal trainer that I expect will appeal even more with web feet, for those of aquatic inclinations.
Some details:
The Hydroplane is the 6th generation model of the successful P92.
Takeoff run is spec'd at under 200 meters, along with "an impressive climb rate" from its 100 hp Rotax engine. And I wonder how the Eaglet's landing performance, for example (26 kts., full flaps, no power) will translate to the water and extra weight.
The Hydro will be produced at Tecnam’s new composites production facility, home to both the Tecnam P2008 and Tecnam P2010 four-seat GA up-and-comer, in Capua, Italy.
There's nothing much online about it yet; I'm hoping it will make it to Sebring mid-month, or Sun 'n Fun in April.
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| Jim Lee finishing the NASA speed run. photo courtesy NASA. |
Gliders and the Impossible Turn
Also just heard from friend and soaring pilot/instructor/longwing trendsetter Jim Lee, last heard from when he flew the only conventionally-powered aircraft in the NASA Green Flight Challenge last fall that won Pipistrel's Taurus Electro G4 a cool $1.35 million prize.
Jim acquitted himself admirably with the Phoenix motorglider at that event.
He dropped me an e-note to add his glider-centric take on my Impossible Turn post here of a couple days ago.
Take it away James:
"For one, in any aircraft, don't follow the centerline of the runway (after) take off unless required by parallel runways or tower ops. Veer downwind of the runway on climb out, then if the engine quits, you only have to make a 180, not a 270.
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| Pretty Phoenix. photo courtesy Jim Lee |
Jim heads up PhoenixUSA out of Melbourne, Florida. I've flown and reported on the Phoenix and it is one wonderful all-around dreamship.
4 comments:
James,
To make the "impossible" turn, you need either high L/D or low airspeed (or both, like a sailplane).
L/D helps in the obvious way: if you double L/D, you halve the altitude loss.
Airspeed has a much more powerful effect: it's a lot easier to make the "impossible" turn in a slow-moving aircraft. In fact, the degree of difficulty (so to speak) is proportional to the square of the airspeed.
Since humans have almost no intuition for square laws, this creates two kinds of risk: the big risk is that a pilot who is accustomed to being able to make the turn in slow aircraft (like gliders or LSAs or C-152s) may try it in something faster (a Bonanza or light twin) and be VERY surprised by how badly that works (or doesn't work); the lesser risk is that a pilot who is accustomed to faster aircraft may land ahead, into housing or otherwise unsuitable terrain, in a slow-moving aircraft that could easily have made the turn.
Why a square law? Because the time required to make the turn at a given g (bank angle) is proportional to the airspeed, and for a given L/D the sink rate is also proportional to the airspeed, so the altitude lost is proportional to the airspeed squared.
Let's put numbers on it. To get back to the runway centerline means turning a 270, then a 90 in the other direction - a total of 360 degrees of turn if you ignore the time required to reverse the roll.
If you make a 30 degree banked turn at 50kt, it will take you 33 seconds to complete that turn sequence. At an L/D of 10 (in the turn - equivalent to about 12 in straight flight), you will theoretically lose a minimum of 280 feet of altitude in completing the turn. This is consistent with Jim Lee's observation about LSAs: he says 300 feet minimum, and in the real world you wouldn't need to get an LSA all the way back to runway centerline.
If you do the same maneuver in an aircraft that needs to do 75kt in the turn (1.5x faster), you will take 50 seconds (1.5 times as long), but you will lose at least 630 ft in the process - over twice as much! You could compensate for the faster aircraft with more L/D, but you'd need to go from a turning L/D of 10 to 22.5to compensate for the extra speed!
If you do it in an aircraft that turns at 100kt, the numbers become 66 seconds and 840 ft. An accomplished LSA pilot trying to turn back in a Bonanza is in for a nasty surprise!
But - a Bonanza pilot can be VERY surprised to see what can be done by an accomplished pilot in an LSA.
Of course, if you have a typical sailplane, it will make the turn at 50kt with an L/D of 35, still taking 25 seconds, but with a theoretical minimum altitude loss of about 80ft! This is again consistent with Jim's observation about sailplanes - remember that I'm assuming 360 degrees of turn, but a simple 180 back to an open field (not runway centerline) would take half as much, or about 40 ft.
(And please, folks, don't try any of this at home: those are minimum altitude losses, and in any case your aircraft won't match those numbers!)
Cheers,
Thomas
Here, let's summarize:
Turning L/D: 10
Speed: 50kt
Time: 33s
Altitude loss >= 280 ft
Speed: 75kt
Time: 50s
Altitude loss >= 630 ft
Speed: 100kt
Time: 66s
Altitude loss >= 840 ft
- Thomas
James,
Can we delete my last comment? I got one of the numbers wrong! At 100kt, things are even worse than I said before. Bottom line: in an LSA the "impossible" turn should be quite practical perhaps a half minute after liftoff; in something like a Bonanza you may need to be at pattern altitude first!
Here's the correct summary:
Turning L/D: 10
Speed: 50kt
Time: 33s
Altitude loss >= 280 ft
Speed: 75kt
Time: 50s
Altitude loss >= 630 ft
Speed: 100kt
Time: 66s
Altitude loss >= 1,115 ft
- Thomas
Thanks Thomas, appreciate the as-always insightful analysis and info!
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