The Waco F series is a series of American-built general aviation and military biplane trainers of the 1930s from the Waco Aircraft Company. The Waco 'F' series of biplanes supplanted and then replaced the earlier 'O' series of 1927/33. The 'F' series had an airframe which was smaller and about 450 pounds (200 kg) lighter than the 'O' series, while continuing to provide accommodation for three persons in tandem open cockpits. A similar performance to the earlier model was obtained on the power of smaller and more economical engines. The initial models were the INF (125 hp (93 kW) Kinner engine), KNF (100 hp (75 kW) Kinner) and the RNF (110 hp (82 kW) Warner Scarab), all of which had externally braced tailwheel undercarriages. Many further sub-models followed with more powerful engines of up to 225 hp (168 kW). The most powerful in the range was the ZPF of 1936/37, intended for executive use. The 'F' series was popular with private owner pilots for sporting and other uses and continued in production through the late 1930s. The tandem cockpit UPF-7 was adopted by the Civilian Pilot Training Program and continued in production until 1942 by which time over 600 had been built. The 1934 model YMF was substantially redesigned with a longer and wider fuselage, larger rudder and other structural changes, and put into production in March 1986 by WACO Classic Aircraft of Lansing, Michigan as the YMF-5. Over 150 YMF-5s were completed as of 2017 with new examples being built to specific orders. The WACO Aircraft Company of Ohio Inc had built three replicas by December 2011, which they designated MF. Variants Listed in approximate chronological order (per Simpson, 2001, p. 573) First letter of designation refers to engine installed. From 1936 Waco added year suffixes to designations—e.g. YPF-6, YPF-7, with the numeral being the last digit of the model year. INF 125 hp (93 kW) Kinner B-5, certified ATC# 345 on 2 August 1930. KNF 100 hp (75 kW) Kinner K-5, certified ATC# 313 on 12 April 1930. RNF 110 hp (82 kW) Warner Scarab, certified ATC# 311 on 7 April 1930.[5] PCF 170 hp (130 kW) Jacobs LA-1 and new cross-braced undercarriage, PCF-2 certified ATC# 473 on 2 October 1931 PBF as PCF with 'B' wings QCF 165 hp (123 kW) Continental A70, QCF-2 certified ATC# 416 on 9 April 1931 UBF 210 hp (160 kW) Continental R-670 UMF 210 hp (160 kW) Continental R-670A and longer and wider fuselage, and larger fin YMF 225 hp (168 kW) Jacobs L-4 YPF-6 and YPF-7 225 hp (168 kW) Jacobs L-4 ZPF-6 and ZPF-7 285 hp (213 kW) Jacobs L-5 UPF-7 (Specifications below) tandem trainer with wide-track undercarriage and 220 hp (160 kW) Continental R-670 (designated PT-14 by the USAAC)
