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Sunday, 24 March 2013

Piper PA-38-112 Tomahawk


PIPER PA-38 TOMAHAWK
Jagriti Srivastava








The Piper PA-38-112 Tomahawk is a two-seat, fixed tricycle gear general aviation airplane, originally designed for flight training, touring and personal use.
The PA-38 Tomahawk (nicknamed Tommy for short) was the first all new two seat trainer built by one of the USA's big three GA manufacturers in almost three decades when it was introduced.
The PA-38-112 Tomahawk was designed as a relatively inexpensive to acquire and operate two seat trainer to tackle the firmly established definitive basic trainer in the 1970s, the Cessna 150 and 152, and to take over the spot in Piper's model range then occupied by two seat variants of the PA-28 Cherokee series.


DEVELOPMENT

The Tomahawk was Piper's attempt at creating an affordable two-place trainer. Before designing the aircraft, Piper widely surveyed flight instructors for their input into the design. Instructors requested a more spinnable aircraft for training purposes, since other two-place trainers such as the Cessna 150 and 152 were designed to spontaneously fly out of a spin. The Tomahawk's NASA GA(W)-1 Whitcomb airfoil addresses this requirement by making specific pilot input necessary in recovering from spins, thus allowing pilots to develop proficiency in dealing with spin recovery.


PRODUCTION

TOMAHAWK COCKPIT
The Tomahawk was introduced in 1977 as a 1978 model. The aircraft was in continuous production until 1982 when production was completed, with 2,484 aircraft built.
The 1981 and 1982 models were designated as the Tomahawk II. They incorporated improved cabin heating and windshield defroster performance, an improved elevator trim system, improved engine thrust vector, 100% airframe zinc-chromate anti-corrosion treatment, better cockpit soundproofing, larger 6" wheels and tires for greater propeller ground clearance and improved performance on grass and dirt runways, among other enhancements.

SAFETY RECORD
A Piper PA-38-112 Tomahawk showing its rectangular wing planform. Stall strips can be seen as rectangular bumps along the aircraft's leading edge.
According to the Aircraft Owners and Pilots Association Air Safety Foundation, which published a Safety Highlight report on the Piper Tomahawk, the Piper Tomahawk has a one-third lower accident rate per flying hour than the comparable Cessna 150/152 series of two-place benchmark trainers. However, the Tomahawk has a higher rate of fatal spin accidents per flying hour. The National Transportation Safety Board (NTSB) estimated that the Tomahawk's stall/spin accident rate was three to five times that of the Cessna 150/152.
According to the NTSB, the Tomahawk's wing design was modified after FAA certification tests, but was not retested.Changes included reducing the number of full wing ribs and cutting lightening holes in the main spar.The aircraft's engineers told the NTSB that the changes made to the design resulted in a wing that was soft and flexible, allowing its shape to become distorted and possibly causing unpredictable behavior in stalls and spins.The design engineers said that the GAW-1 airfoil required a rigid structure because it was especially sensitive to airfoil shape, and that use of a flexible surface with that airfoil would make the Tomahawk wing "a new and unknown commodity in stalls and spins."
Airworthiness Directive 83-14-08 issued in September 1983 mandated an additional pair of stall strips to be added to the inboard leading edge of the PA-38 wing to "standardize and improve the stall characteristics".
Because of its stall and spin characteristics, the PA-38 earned the nickname "Traumahawk" from some pilots and instructors.

ROLES
Besides being a widely used primary trainer, it is also an effective budget cross-country aircraft for two persons with its spacious and comfortable cabin. Though it shares similar performance and costs of operation to the Cessna 152, the PA-38 has more shoulder room. It also has good cabin ventilation, using automotive-style air ducts. Common cruise speeds range from 90 to 110 knots (167 to 204 km/h).


SPECIFICATIONS (PA-38-112 Tomahawk II)

GENERAL CHARACTERISTICS
Crew: 2
Length: 23 ft 1¼ in (7.04 m)
Wingspan: 34 ft 0 in (10.36 m)
Height: 9 ft 0¾ in (2.76 m)
Wing area: 124.7 ft² (11.59 m²)
Airfoil: NASA GAW-1
Empty weight: 1,128 lb (512 kg)
Max. takeoff weight: 1,670 lb (757 kg)
Powerplant: 1 × Avco Lycoming O-235-L2C air-cooled flat-four piston engine, 112 hp (83.5 kW)

PERFORMANCE
Never exceed speed: 159 mph (138 knots, 256 km/h)
Maximum speed: 126 mph (109 knots, 202 km/h) at sea level
Cruise speed: 115 mph (100 knots, 185 km/h) at 10,500 ft (3,200 m) (65% power)
Stall speed: 56.5 mph (49 knots, 91 km/h) (IAS), flaps down
Range: 539 miles (468 nmi, 867 km) at 10,500 ft (3,200 m), (65% power)
Service ceiling: 13,000 ft (4,000 m)
Rate of climb: 718 ft/min (3.65 m/s)


COUNTRY OF ORIGIN  
United States of America

POWERPLANTS  
One 85kW (112hp) Avco Lycoming O-235-L2A or L2C flat four piston engine driving a two blade fixed pitch Sensenich propeller.


FLIGHT CHARACTERISTICS

Pilots need special training because of the way the airplane was designed to stall and spin.  The wing design, the same basic section as on the Beech Skipper, was a cutting-edge airfoil - the NASA-generated GA (W)-1 - in the late 1970s. On the Tomahawk airframe, the wing produces aggressive stall characteristics suitable for teaching primary students about stall recognition and recovery. However, that design led to a higher incidence of stall/spin accidents, perhaps because the airplane cannot simply fly itself out of a spin like other trainers - it wasn't meant to, so that students would learn proper control inputs. This is one airplane where it pays to know the territory.

The Tomahawk controls have a heavier feel, as they were designed to mimic those of a much larger airplane. In addition, the T-tail delivers reduced elevator control response at low airspeeds - and this is actually reflected in the accident reports to a larger degree than stall/spin issues. During the takeoff roll, the elevator becomes effective at around 35 KIAS. If the pilot has been impatient and is holding greater back-pressure in an attempt to raise the nose before this point, the airplane will over-rotate. The same effect reverses on landing, "especially when a headwind shears off"; according to Adam Harris, director of maintenance at East Coast Aero Club at Hanscom Field in Bedford, Mass., who has owned four Tomahawks over the years. These are simply attributes of an airplane that doesn't fit the standard mould, Harris points out. "We rent them to people with 10 hours and they always come back." 

In fact, if you're looking for an airplane to provide a steppingstone to a larger aircraft, the Tomahawk makes a sound choice. You face an easier transition in the long run because of these big-airplane characteristics. 


CROSS-COUNTRY FLIER

The Tomahawk is roomier than you might think, and taller pilots feel more comfortable in this airplane than in a Cessna 152. Ventilation is also better than average, with automobile-style vents blowing cool air at altitude on summer days. The cabin is wider by several inches than other two-seat airplanes, so you needn't be intimate with your passengers.

The airplane's greatest utility is as a day-tripper. Paul Diette of Mansfield, Mass. bought his 1982 Tomahawk II for trips around New England with his wife - trips that take less than three hours and only require light bags. The airplane has proven perfect for the mission: Places like Martha's Vineyard and Bar Harbour, Maine, are reachable in half the driving time.

Usable fuel is 30 gallons, and during cruise Diette figures he bums between six and seven gallons per hour. He typically flight plans a true airspeed of 105 knots. Endurance is about 3.5 hours with an hour reserve - with full fuel you can carry roughly 325 additional pounds of pilot, passenger, and baggage, based on the empty weight of a reasonably equipped Tomahawk (around 1165 pounds). It goes over gross quickly (it is a two-seat aircraft, after all), but because of the size of the cargo area, light-but-bulky items, such as an Adirondack chair that Diette flew home after a successful shopping trip, can be handled. 











Regards,

Jagriti Srivastava [B.Tech ] 
Web Developer / Blog Master 


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