August 1, 2002
JULIE K. BOATMAN
Speed rules. And with all the mods out there to turn your bugsmasher into a rocket, you may wonder how money turns into speed. There are speed enthusiasts who argue that you should see one knot of speed gain for every $1,000 spent on modifications. If only it were that easy.
Some mods work well on particular airframes, and some don't work at all. You may spend thousands on contraptions with funny names and the glue to stick them on, and come up empty-handed. And you're almost never going to get that money back when it comes time to sell.
So why do pilots go for the elusive speed? Because like the Holy Grail, the Fountain of Youth, and the Lost Dutchman Goldmine, we've heard tales of riches — and speeds that leave their hangar buddies in the dust. And enough of these stories are true to keep us in the quest for speed.
We had an opportunity to follow an airplane through two iterations of power and speed mods — a rare chance to witness firsthand the rebirth of one very average Piper Cherokee 140 into, yes, a 140 that can reliably beat 140 mph true airspeed.
Laminar Flow Systems, a division of Power Flow Systems, borrowed N140HC from customer Jim Rhoads to develop modifications to boost performance in PA-28-series aircraft. No aircraft that's been flying for more than 30 years, as 0HC has, comes without flaws. We reviewed the Power Flow Systems' tuned exhaust on 0HC last winter (see " Pilot Products," February Pilot), and we found the power increase produced by the system to be substantial.
At that time, the airplane worked flawlessly. During the testing for this review, however, a carburetor heat cable that had been previously repaired began binding, leaving the valve progressively farther open each time the carb heat was applied. This affected our tests of the Laminar Flow speed mods, since the problem wasn't addressed until after the airplane returned to the company's headquarters.
Even with this underlying problem, the airplane gained notably with the speed mods. These mods included aileron and flap gap seals (to cover the space between the fuselage attach points and the flight controls), flap hinge fairings, wing-smoothing and fuel-tank fairings, a nose-gear fairing, and main-gear speed pants (with FAA certification pending during the test — the rest of the mods were certified at the time of testing).
We followed roughly the same profile during our climb as in the previous test, but flew a 92 to 95-mph target speed for better engine cooling (V Y is 85 mph). We leaned the mixture after passing through 5,000 feet, according to Piper's recommendation. Our average rate of climb, with the extra 7 mph, was 475 fpm from 5,000 to 7,500 ft — only 25 fpm less than the prior test. The company reports up to 100 fpm additional climb at V Y from the speed mods in their own testing. For better cooling, visibility, and greater groundspeed, it seems like the extra speed is an adequate tradeoff.
However, the Laminar Flow mods are optimized for cruise and performance at top speed. Prior to installation of the aerodynamic mods, the tuned exhaust system-equipped 0HC topped out at 118 mph indicated, and 134 mph true at 8,500 ft msl, minus 1 degree Celcius, and 2,645 rpm. The Laminar Flow-equipped 0HC gained 50 rpm (even with the carb heat cable problem) and indicated 124 mph, with a TAS of 140 mph.
Down lower, with increased rpm available, we saw the TAS climb to 147 mph (at 4,500 ft, minus 4 degrees C, and 2,750 rpm). Fuel flows were 11.4 gph at this lower altitude, versus 10.8 gph at 8,500 ft. We had flown the airplane from Frederick, Maryland, to Lancaster, Pennsylvania, for the test, and on the way back, there were times when the airspeed indicator nudged 142 mph, for a TAS around 150 mph. However, we couldn't hold this speed; the 147-mph figure is the honest conclusion.
One big question: An rpm above 2,700 says "redline," and some may argue that it's not fair to claim speed gains at unsustainable rpm. Darren Tillman of Power Flow/Laminar Flow responds: "Because speed mods enhance performance so greatly, it is more likely the engine will exceed the redline limitation up to a much higher altitude than they are used to. It is possible to repitch the propeller to more of a cruise pitch." The owner can trade climb performance for extra speed in cruise and keep the prop below redline at the same time. The prop was left in the original pitch during both tests.
Before any modifications were made, the airplane performed well below pilot's operating handbook values. With both the tuned exhaust and Laminar Flow mods, the airplane matched book speeds at 75-percent power — but only using fuel flows commensurate to 65-percent power. The package added a little more than 17 pounds to 0HC's empty weight.
If you want the fastest 140 on the block, the Laminar Flow mods make a good argument. We gained 6 mph (roughly 5 kt) at cruise, were able to climb at faster groundspeeds, and added some low-speed handling improvements in the process. The total cost of the Laminar Flow mods to 0HC comes to $3,410 (estimated retail price; discount kits will be available). So if every Cherokee 140 on the ramp takes to the mods like 0HC, the $1,000-to-knot ratio is easily beat by the package.
For more information, contact Laminar Flow Systems, 1585 Aviation Center Parkway, Hangar 804, Daytona Beach, Florida 32114; telephone 877/693-7356; fax 386/248-1587; or visit the Web site ( www.powerflowsystems.com).
Telex's latest active noise reduction (ANR) headset, the Stratus 50-D, attacks noise from both angles. The cushy, sink-down-into-'em-and-get-comfy ear cups supply passive noise protection, and control the squish factor with a three-position dial that lets you adjust the headset's clamping action to fit your taste. The new headset offers analog ANR and digital tonal ANR. This is the second-generation digital ANR headset produced by Telex — digital means that a computer chip inside the headset samples ambient noise and anticipates that the noise will continue. So, instead of reacting to a noise, like analog ANR headsets do, the Telex digital system works "proactively," according to a company spokesman. Telex claims that the Stratus gives you 50 dB, or more, of active and passive noise reduction for a total package that compares favorably in cockpit use to the arguably top-of-the-line Bose Aviation Headset X models.
The Stratus 50-D lists for $875, with average street prices just under $800. The headset is robust; the model we tested weighed 23.2 ounces without the battery box. A cord to power the headset off of the airplane's electrical system is also included; the headset retains its passive features — and still keeps out most of the noise — if power is lost. For more information, contact Telex, 12000 Portland Avenue South, Burnsville, Minnesota 55337; telephone 952/887-5586; fax 952/887-5595; or visit the Web site ( www.telex.com).
After four years of producing PMA7000-series audio panels, PS Engineering has rolled several "customer favorite" features into one new unit, the PMA7000B. The panel includes all-push-button controls, a six-place Intellivox intercom expandable to 10-place, full duplex mode for AirCell or other wireless interfacing, split modes for com 1, 2, and 3, and dual independent music mode with SoftMute (PS Engineering's proprietary muting system that senses incoming radio transmissions). Retail price is $1,895, which includes the marker beacon receiver. For more information, contact PS Engineering, 9800 Martel Road, Lenoir City, Tennessee 37772; telephone 865/988-9800; fax 865/988-6619; or visit the Web site ( www.ps-engineering.com).
Unless otherwise stated, products listed herein have not been evaluated by AOPA Pilot editors. AOPA assumes no responsibility for products or services listed or for claims or actions by manufacturers or vendors. However, members unable to get satisfaction regarding products listed should advise AOPA. To submit products for evaluation, contact: New Products Editor, AOPA Pilot , 421 Aviation Way, Frederick, Maryland 21701; telephone 301/695-2350. Links to all Web sites referenced in this issue can be found on AOPA Online ( www.aopa.org/pilot/links.shtml).
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