Design beginning in the mid 1970s to FAA FAR Part 23 the first Cresco, (Latin for “I grow”) flown, ZK-LTP, became airborne in February 1979. During development, feedback from operators of the Fletcher aircraft regarding areas in which the Fletcher was lacking was taken into account, however the strength of the original design was retained.

The new aircraft featured a longer fuselage, a massive hopper, enlarged fin and rudder, revised wing with integral fuel tanks (wet wing) and a 600 hp, Lycoming LTP 101 turbine. The Cresco retained all the good features of the Fletcher.

Although appearing very similar to the FU 24 Fletcher at first glance, the Cresco was actually a much bigger machine and improved in many ways. With its tricycle landing gear and rear mounted hopper the Cresco is unique in agricultural aircraft and, through this configuration, allows for safe operations off these sloping hill strips. The Cresco has the advantage of forward visibility and wind gust capabilities lacking in tail dragger aircraft with forward mounted hoppers.

All metal semi monocoque construction, comprising of frames and longerons covered by pre-formed aluminium alloy skins. Wing single spar cantilever construction with sheetmetal ribs covered by pre-formed aluminium alloy skins with the centre wing having no dihedral and outer with 8 degree dihedral. Dual side by side controls. Fixed tricycle landing gear with a wide track and long stroke oleos designed for rough fields and providing a soft ride. Rear mounted hopper independent of the fuselage. Three-blade Hartzell fully reversible prop. Superb visibility with the cockpit forward of the wing and hopper to the rear rather than in front. No handling vices. Cockpit environmental structure stressed to 25g.

After several years of design and construction ZK-LTP, the prototype 08-600 Cresco took to the air on the 28th February 1979 powered by a 600 shp Lycoming LTP101-600A-1A turbine engine. This was the first flight in the world of an aircraft designed from the outset as a turbine powered agricultural aircraft.

Configured as a dual control aircraft with a 62.5 cu. ft. hopper it differed from future examples by having a full flying tail-plane (much like the FU-24) and no dorsal fin.

After a bright start to the certification process trouble stuck on the 10th December 1979 when, after difficulties during a test flight, the pilot elected to parachute to safety and consequently ZK-LTP was completely destroyed as it impacted the ground.

It was June 1980 before the second prototype ZK-LTQ s/n 002 took to the air for the first time and the certification process continued. Significantly ZK-LTQ unlike s/n 001, sported a new fixed tail-plane and a dorsal fin.

By January 1981 the certification process was complete, NZ Certificate of Type Approval NZ CTA A-11 was granted as the 08-600 Cresco, and production had commenced with s/n 003 ZK-LTR first flying on the 19th January 1981.

In the steep New Zealand hill country, “operating” means operating from an unimproved landing strip; often on the side of a hill with a flat spot at the top to load. With GPS to help make accurate dispersal runs, the aircraft will often be back for another load in less than 4 minutes. From brakes on to brakes off, the loading operation is completed in around 7 seconds and power is applied for the takeoff run. One unforeseen problem arose with the introduction of the Cresco: the aircraft was dispersing material faster than the trucks could deliver it to the aircraft.

Production had no sooner commenced when it was slowed considerably over the next decade due to a downturn in the farming sector. Only six further examples were produced between 1982 and 1992.

S/n 004 ZK- JAD the first 700 hp and single control variant was produced in January 1983 followed by s/n 005 ZK-LTS in September 1987. There was some relief in 1990 when three examples were produced for the Department of Plant Protection in Bangladesh. Next off the line was s/n 009 the last LTP101 powered variant (ironically like the prototype also ZK-LTP) which first flew in October 1992.

In 1992 the customer for s/n 010 requested replacement of the Lycoming LTP101 Engine with a Pratt & Whitney Canada PT6A-34AG engine of 750 shp. First flown in November 1992 the modification was an outstanding success and the PWC powered Cresco became the standard aircraft that PAC produced as the Cresco 750.

When PAL changed ownership in late 1995 the first continuous Cresco 750 production commenced with s/n 012 ZK-TMO first flying on the 15th February 1996, and by the time the year was out four aircraft had been completed. A further five examples were completed in 1997 including several milestone aircraft:

S/n 019 the first aircraft with the “big” hopper mouth and gatebox, s/n 020 the first aircraft with the new extruded spar caps and s/n 021 the first utility version produced.

The next significant milestone was the production of the first utility parachuting variant s/n 024 in September 1999, which contributed to the subsequent development of the new P-750 XSTOL.

It is able to take a pilot and twelve skydivers to 14,000 ft (4,267m) in 12 minutes.

Modifications for the skydiving role include factory installed special steps, external jump door, grab rails and a large air scoop cowling to allow the engine to obtain full power at altitude.

Production continued through the early 2000s and in 2002, the highest production year to-date, seven examples were produced cumulating in s/n 036 ZK-TTS.

Of the last 10 airframes produced five have been agricultural variants and five utility parachuting variants.

PAL has upgraded four of the early Lycoming LTP101 powered aircraft to PWC PT6A-34AG 750 shp status.

This unique and special aircraft is no longer in production.

Gallery

08-600
Engine: AVCO-Lycoming LTP 101/600A-1A turboprop, 599 shp
Prop: Hartzell HCB3TN-3D/T1028H, 8.5 ft
Hopper cap: 62.5 cu.ft (1770 lt), 4100 lb (1860 kg)
Range (no res): 460nm
Ceiling MAUW: 15,500 ft
ROC 6450 lb: 880 fpm
ROC 7000 lb: 745 fpm
Stall: 54 kt
Max speed: 145 kt
Cruise 75%: 127 kt
Empty wt: 2560 lb
MTOW, Norm; 6450 kg
MTOW, Ag; 7000 lb
T/O dist 7000 lb: 1317 ft
T/O dist 6450 lb: 1058 ft
Length: 36.33 ft (11.08m)
Height: 11.9 ft (3.63m)
Wing span: 42 ft (12.8m)
Wing area: 294 sq.ft (27.33sq.m)

08-600 Cresco
Engine: TPE331-1-101L, 665 shp
MTOW std: 5800 lb
MTOW ag: 6500 lb
Vne: 181 kt
Va: 122 kt
Type certificate: NZCAA A-9
Certificate issued: 10 Jun 71

Cresco 750
Engine: Pratt & Whitney PT6A-34AG, 750 hp
Propeller: Hartzell 3 Bladed fully feathering and reversible
Wing Span: 42 ft / 12.8 m
Fuselage Overall Length: 36.2 ft / 10.9 m
Fuselage Maximum Width: 48 in / 1.22 m
Fuselage Maximum Height: 60 in / 1.52 m
Wing Aspect Ratio: 6.0
Basic empty weight: 2,950 lb / 1,338 kg
Max. Take-Off Weight (Standard): 6,450 lb / 2,925 kg
Max. Take-Off Weight (Agricultural): 8,250 lb / 3,742 kg
Max. Landing Weight: 6,450 lb / 2,925 kg
Max. Useful Load (Standard Category – 1 crew, 2.5 hrs fuel): 2,450 lb / 1,111 kg
Max. Useful Load (Agricultural Category – 1 crew, 1 hrs fuel): 4,750 lb / 2,154 kg
Max. Structural Hopper Load: 4,100 lb / 1,859 kg
Disposable load: 5,400 lbs / 2,449 kg
Working speed: 136 kts / 240 kph
Hopper capacity: 500 USG / 1900 litres
Hopper outlet size: 41″ / 1340 mm wide
Firebombing discharge rate: up to 900 lt/sec
Never Exceed Speed (VNE): 176 Knots / 325 kph
Design Cruising Speed (VC): 140 Knots / 259 kph
Max. Manoeuvring Speed (VA): 126 Knots / 233 kph
Max. Flap Retracted Speed: 85 – 90 Knots / 157 – 166 kph
Stall Speed (Idle Power) At Max. Weight: 57 Knots / 105 kph
Range – Normal: 420 Miles / 675 km
Endurance – Normal Configuration: 2.7 hr
Average Fuel Consumption Per Hour: 48 US/Gal / 180 lt
Take-Off Distance To 15 M (50 FT) ISA: 1,065 ft / 325 m
Landing Distance From 15 M (50 FT): 1,398 ft / 426 m
Max. Rate Of Climb At Sea Level: 1,560 fpm
Max. Rate Of Climb at 8,000 ft: 1,060 fpm
Max. Rate Of Climb at 14,000 ft: 680 fpm
Max. Operating Altitude: 25,000 ft
Service Ceiling (At Max. Weight): 25,000 ft
Max. G: +3.56 / -1.42
Wing Loading: 104 kg/sq.m / 21.9 lb/sq.ft
Power Loading: 0.25 shp/kg / 0.11 shp/lb
Ailerons: Plain 25 deg up travel, 10 deg down travel
Vertical Tail Surface: Fixed fin, horn balance rudder
Rudder Deflection: ± 30 deg
Horizontal Tail Surface: Fixed plane with elevator
Elevator Deflection: 30 deg up, 8.5 deg down
Landing Gear Track: 12.2 ft / 3.71 m
Wheel and Tyre Size: 8.50 x 6 nose 8.50 x 10 main
Cargo Payload: 3,136 lb / 1,435 kg
Large Door Size: 39” x 37” / 0.99 m x 0.94 m
Maximum Cabin Height: 4.21 ft / 1.28 m
Maximum Width: 3.5 ft / 1.06 m
Floor Length: 10.25 ft / 3.12 m
Total Compartment Length: 11.83 ft / 3.61 m
Total Compartment Volume: 133 cu.ft / 3.79 cu.m
Application rate typically 30 tonnes per hour
Swarth width: 88 ft / 27m
Aircraft Inspection Cycle: 100 hours inspections
Wing spar life: 16,000 hours
Wing strap life: 8,000 hours

08-600 Sky dive
Engine: PT6A-34
Ceiling: 24,000 ft
Crew: 1
Pax: 11
Time to 20,000 ft: 12 min