Wills Wing / Grumman Comparison

 

By Stuart Broce

 

August, 1996:

 

          As a recreational paraglider pilot, and a professional fighter pilot, I often get asked by people from both communities about the ‘other’ type of flight. From the interest shown by fellow paraglider pilots, I suspect that more people wonder how the two types of flying compare.

          A few weeks ago, I logged and hour and a half each flying a Wills Wing AT 125 and an F-14D Tomcat. Granted, there are few similarities between a fourth-generation fighter and a paraglider, but let’s not split hairs—it was a perfect opportunity to compare the flying qualities of the two aircraft.

          Fighter first: The F-14D is a supersonic, two-place fighter manufactured by the Grumman Aerospace Corporation. It is powered by two afterburning General Electric turbofan engines. With its variable-sweep wings, the Tomcat is capable of in-flight aerodynamic reconfiguration, allowing flight beyond twice the speed of sound, yet providing approach speeds low enough to land on a boat. These features allow the jet to patrol from the decks of aircraft carriers to just about any place on Earth.

          The Wills Wing AT 125 is a single-place, Class 1 paraglider made by Wills Wing, Inc. It’s fabric construction also allows for in-flight aerodymnamic reconfiguration and remarkable portability.

          Inherent design philosophy in each aircraft is very different. Not surprisingly, each aircraft performs its intended mission significantly better than the other. The AT 125 is a very capable recreational paraglider , but it wouldn’t fare well in combat. Tactically, a paraglider pilot could have the initial advantage of surprise and low heat signature, but effectiveness would be negligible due to limited ordnance carrying capacity, and poor survivability. The F-14 can down multiple enemy aircraft from a perch in a different time zone and also perform a devastating ground attack, but it glides like a Coke machine and only comes in gray—factors that seriously limit its recreational soaring appeal.

          Performance figures back up differences in the two designs. The Tomcat is powered—its motors crank out nearly 60,000 pounds of dynamic thrust in full afterburner. Coupled with large, hydraulically-boosted flight control surfaces, the motors can shove the F-14 through the sky with remarkable agility for a 54,000 lb. (half fuel load) jet. Top speed is advertised as MACH 2.4, but flying near that speed may peel lots of expensive paint off the nose and will, most certainly, upset the squadron maintenance officer. Trust me.

          The AT 125 approaches MACH 0.035 with the speed stirrup fully engaged, but its low-speed handling is remarkable, allowing for landing speeds near zero.

          In terms of turn radius, the AT 125 blows the Tomcat away. Max performance figures for the F-14’s turning ability are classified, but it’s safe to say that the turn performance of AT 125 makes it the obvious choice for sites with tight lift bands. Turn radius, while small and fairly constant throughout the Wills Wing’s speed range, varies in the Tomcat from a few thousand feet to several miles as you accelerate toward maximum velocity. Also, the AT 125 is much more enjoyable at its turning limit because the associated g-loading, approximately 2 g’s compared to the Tomcat’s 6.5 g’s,  is more conducive to sightseeing because of the reduced strain on the body and significantly reduced chances of GLOC (g-induced loss of consciousness).

          Gliding performance is the F-14’s biggest disadvantage. Deceleration from supersonic to landing speed in the big jet causes the wings to sweep forward from 68˚ aft of perpendicular (to the longitudinal axis) to 20˚. Wing loading on the Tomcat is about 90 pounds per square foot with the wings fully forward in their ‘best glide’ position. The AT 125 boasts a wing loading of less than 1 pound per square foot, even with my 220 pounds aboard. All but the most severe turbulence is unremarkable in the F-14. The AT 125 responds to even the slightest variations in lift, but remains stable even in conditions that sometimes send Class 2 gliders toward the LZ.

          The Tomcat has a power-off glide speed of about 250 knots, minimum—any less and the engines stop windmilling, cutting off hydraulic power for the flight controls. This speed translates into a glide ratio comparable to the AT 125, but with the associated 5000 feet per minute rate of descent, local winds and/or thermal activity would have to be epic to significantly extend flight time. Unfortunately, an F-14 with its engines off is uncontrollable at landing speeds so pilots really take their chances when operating the jet down low with the motors off. The AT 125 has a no-wind rate of descent of about 2-300 feet per minute—obviously the better pick for recreational soaring and unpowered landings.

          The F-14 does, however, have a viable, built-in ridge-soaring and thermalling capability. Each ejection seat contains a parachute that deploys automatically upon ejection. With a strong (35-knot plus) breeze and cooperative topography, these steerable chutes could theoretically be used to log some post-ejection soaring time. The disadvantages of this system are many, however. The harness is just too uncomfortable to enjoy any maneuvering flight (such as observing the ridge rules that would apply when you have to share a site with your radar intercept officer) especially if there is post-ejection trauma such as spinal compression or flail injury. And, although you could get to some prime sites very rapidly, the F-14 just costs too darn much ($70 million a pop) to punch out of every time your favorite site goes off. It would be nice if paraglider technology could be utilized in the ejection system, especially in wartime when flying within gliding distance of friendly forces. I didn’t ask Wills Wing about it, but I doubt that their gliders are stressed for 450-knot opening shock.

          In terms of pilot comfort, the paraglider harness beats the cockpit of the F‑14, hands down. The Tomcat’s cockpit is well laid out for its intended purpose, but the ejection seat isn’t very relaxing. Seat padding is almost non-existant, and the backrest angle forces the occupant uncomfortably upright. Throw in the g-suit, harness and oxygen mask required for flight and things get even more uncomfortable. I contacted Grumman about this and, although their customer service department was very helpful, there are no current plans to improve aircrew comfort. They cited the need to minimize spinal compression when asked about the seat, but I suspect it was just designed to keep us from enjoying the ride too much.

          The Wills Wing harness is luxurious by comparison. Using the various adjustment straps, I was able to find an agreeable setup that allowed me to forget about the harness and enjoy my flight. Some of the adjustments work their way loose near the end of each flight, though, due to inadequate adjustment device design. My harness is a couple of years old, though—I assume Wills Wing has addressed this problem on more recent designs.

          For flight instrumentation, I’ll have to give the nod to the F‑14. I refuse to sell my car to finance a Swiss wonder-vario, but I’d bet the Tomcat’s HUD (Head Up Display) can provide more information. Undoubtedly, flying in instrument conditions and at night is probably be more enjoyable in the Tomcat, although I’ve tried neither in the AT 125. Both aircraft have optional GPS units, so neither has a real edge with navigation.

          Comparing the two types of flying involves more than aircraft performance, hardware and flying comfort, though. Intangibles such as sounds and smells are much more enjoyable in the paragliding environment. The scent of a rubber oxygen mask and the roar of an air-conditioning system just don’t compare to the varied odors of wild foliage, the ocean, and the medley of sounds that make local soaring sites so enjoyable.

          Which aircraft would I rather fly? Each is capable of providing great enjoyment in its own domain. The Tomcat rocks—there is absolutely nothing subtle about it. It converts kerosene and air into copious heat, noise and adrenaline. The most rowdy summer thermals in the paraglider pale compared to a forty thousand feet-per-minute climb. Twenty seconds of inverted, near-weightless flight pulling over the top of a 40,000 foot vertical climb does wonders for the soul. So does a 5 g inverted pull, 200 feet over a mountain top and down the other side at 600 knots (head’s up in Owen’s Valley). As a cross-country aircraft, it’s unsurpassed with its bubble canopy and speed.

          To be honest, though, most operational flights in the Tomcat aren’t unbridled fun. Fuel conservation is the main mission when the only place to land is bobbing around in a storm two hundred miles away—especially at night.

          Flying the AT 125 can be just as enjoyable as cutting loose in the F14, however. The flight controls on the Wills Wing are more intuitive and strangely satisfying in a visceral way—arms outstretched in a wanton romp with the wind. Ironically, the utilization 20 pounds of fabric and lines to soar strikes me as the pinnacle of aviation technology. Exploring beautiful soaring sites and playing with the wind are things you just can’t enjoy in a 600-knot air-conditioned bubble.

 

 

                Grumman F-14D                               Wills Wing AT 125

                                       44,000 lbs.......................... Empty Weight............................. 25 lbs.

                                         38-63 ft................................ Wingspan................................. 32.9 ‘

                                         Variable............................. Wing Area................................ 315 ft²

                                       >70 lbs/ft²......................... Wing Loading........................... <1 lb/ft²

                                       MACH 2.4.................................. V_max................................ MACH 0.035

                                         <100 kts.................................... V_min............................... Approx. 15 kts.

                               Approx. $70 million................ Price (as tested)............. Approx. $0.003 million