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 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, KNF and the RNF , all of which had externally braced tailwheel undercarriages. Many further sub-models followed with more powerful engines of up to. The most powerful in the range was the ZPF of 1936/37, intended for executive use.
Operational history
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. Considerable numbers of 'F' series biplanes, both original and newly built, remain in service.
Variants
Listed in approximate chronological order ;INF: Kinner B-5, Certified ATC#345 on 2 August 1930. ;KNF: Kinner K-5, Certified ATC#313 on 12 April 1930. ;MF : Jacobs R-755, built by WACO Aircraft Company of Ohio Inc by 2011 ;RNF: Warner Scarab, Certified ATC#311 on 7 April 1930. ;PCF: Jacobs LA-1 and new cross-braced undercarriage, PCF-2 Certified ATC#473 on 2 October 1931 ;PBF: as PCF with modified 'B' wings ;QCF: Continental A70, QCF-2 Certified ATC#416 on 9 April 1931 ;UBF: Continental R-670 ;UMF: Continental R-670A and longer wider fuselage and larger vertical fin ;YMF: as UMF with Jacobs L-4 ;YPF-6 and YPF-7: Jacobs L-4 ;ZPF-6 and ZPF-7: Jacobs L-5 ;UPF-7: tandem training version with wider-track undercarriage and Continental radial ;YMF-5: 1986 design roughly based on the YMF, built by WACO Classic Aircraft ;YMF-5D: 2009 improved YMF-5 ; YMF-5F: YMF-5 with Aerocet 3400 amphibious floats ;JW:Two UBF designated XJW-1 were used by the US Navy as hook-up trainers for the Curtiss F9C Sparrowhawk airship-borne fighters. Note: 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.
Operators
Military operators
Guatemalan Air Force - At least 1 Waco YMF-7 received in 1934. Was still in airworthy condition in 1998.
United States Army Air Corps - Adopted the UPF-7 as the PT-14, with one XPT-14 and 13 YPT-14s being purchased, with an additional UPF-7 impressed in 1942 as a PT-14A.
