View source for Kellett KD-1

{{Short description|1930s American autogyro}}
{|{{Infobox aircraft begin
| name = Kellett KD-1
| image = Kellet YG-1B Autogyro (37-381 - N37380) (25340902763).jpg
| caption = Kellett XR-3 modification of YG-1B (KD-1) of U.S. Army preserved at [[Yanks Air Museum]], [[Chino, California|Chino]] airfield California, in February 2016
}}{{Infobox aircraft type
| type = Autogyro
| national origin = United States
| manufacturer = [[Kellett Autogiro Company]]
| designer =
| first flight = [[1934 in aviation|1934]]
| introduced =
| retired =
| status =
| primary user = [[United States Army Air Forces]]
| more users = [[Eastern Airlines]]
| produced =
| number built =
| developed from =
| variants with their own articles =
| developed into = [[Kayaba Ka-1]]/Ka-2
}}
|}
The '''Kellett KD-1''' is a 1930s [[United States|American]] [[autogyro]] built by the [[Kellett Autogiro Company]]. It had the distinction of being the first practical rotary-wing aircraft used by the United States Army and inaugurated the first scheduled air-mail service using a rotary-wing aircraft.
==Development==
Using the experience gained in building [[Cierva]] autogyros under licence the Kellett Autogiro Company developed the KD-1 which was similar to the contemporary [[Cierva C.30]]. It had two open cockpits, a fixed tailwheel landing gear and was powered by a 225&nbsp;hp (168&nbsp;kW) Jacobs L-4 radial engine. The D in the KD-1 designation stood for Direct control, meaning that the rotor was responsible for all control of the machine, so ailerons, wings and elevators were not necessary.<ref>{{cite web |title=Kellett KD-1 |url=http://www.aviastar.org/helicopters_eng/kellett_kd-1.php |website=All the World's Rotorcraft |access-date=24 May 2020}}</ref> This caused distrust from Kellett's test pilots, who refused to fly it. Kellett then hired [[Johnny Miller (aviator)|Johnny Miller]], who thoroughly understood autogyros, as chief test pilot. After successful testing of the prototype, it was converted into a mail-carrying variant designated the '''KD-1A''' which had the front cockpit converted into a baggage compartment and was put into production. It had a three-bladed rotor with folding blades and a number of minor detail improvements. A '''KD-1B''' was a development of the KD-1A, with an enclosed cockpit for the pilot, radio, blind-flying instruments and a landing light, and was ordered and operated by [[Eastern Air Lines]], who hired Miller to fly it.
They inaugurated the first scheduled rotary-wing air-mail service on 6 July 1939 between [[Camden Central Airport]] and [[United States Post Office-Main Branch (Philadelphia)|Philadelphia's main Post Office]].<ref name="NASA">{{cite web |last1=Lewis |first1=W. David |title=The Autogiro Flies the Mail! Realising the dream of flight pp 79-81 |url=https://history.nasa.gov/sp4112.pdf |website=NASA History |access-date=24 May 2020}}</ref>
In 1935, the [[United States Army]] bought a KD-1 for evaluation and designated it the '''YG-1''', a second aircraft followed which had additional radio equipment and was designated the '''YG-1A'''. These two aircraft were followed by a batch of seven designated '''YG-1B'''. In 1942 seven more were bought for use in the observation role as the '''XO-60'''. Six XO-60s were re-engined with 300&nbsp;hp (224&nbsp;kW) [[Jacobs R-915]]-3s and re-designated '''YO-60'''.<ref>[https://books.google.com/books?id=mCYDAAAAMBAJ&dq=Popular+Science+1931+plane&pg=PA129 "ARMY AUTOGIRO"] ''Popular Science'', June 1944, photo of YO-60</ref> One YG-1B was modified with a constant-speed rotor and was re-designated the '''YG-1C''', it was later re-engined with the more powerful R-915 and re-designated again as the '''XR-2'''. The XR-2 was destroyed by rotor ground resonance problems and the evaluation was continued with another modified YG-1B designated the '''XR-3'''.
==Variants==
[[File:Kellett YG-1 at Langley April 1936.jpg|thumb|right|YG-1 (KD-1) at Langley]]
;KD-1
:Prototype, one built
;KD-1A
:Commercial variant with open cockpit and a {{convert|225|hp|kW|abbr=on}} [[Jacobs R-755|Jacobs L-4]] radial engine; three built, one converted from the KD-1.
;KD-1B
:Commercial variant with enclosed cockpit; two built.
;YG-1
:United States Army designation for one KD-1A acquired for evaluation.
;YG-1A
:One aircraft as YG-1 with the addition of radio equipment.
[[File:Kellett YG-1B at Langley - NASA image L-16653.jpg|thumb|right|YG-1B at Langley]]
;YG-1B
:Production aircraft for the United States Army; seven built.
;YG-1C
:One YG-1B modified with a constant-speed rotor for evaluation, later designated the XR-2.
[[File:XO-60.jpg|right|thumb|A Kellett XO-60]]
;XO-60
:Production aircraft for the United States Army with a {{convert|225|hp|kW|abbr=on}} [[Jacobs R-755]] radial engine, seven built.
;YO-60
:Six XO-60s re-engined with a {{convert|300|hp|kW|abbr=on}} Jacob R-915-3 radial engine.
;XR-2
:The YG-1C re-designated after being re-engined with a {{convert|300|hp|kW|abbr=on}} [[Jacobs R-915|Jacobs R-915-3]] radial engine.
;XR-3
:One YG-1B modified to XR-2 standard for evaluation.
;Kayaba Ka-Go prototype
:{{main|Kayaba Ka-1}}
:Based on a KD-1A airframe repaired by Kayaba.
==Operators==
;{{USA}}
* [[Eastern Airlines]]
* [[United States Army Air Forces]]
==Specifications (KD-1B) ==
{{Aircraft specs
|prime units? = imp
|crew=2
|length m=8.79
|length ft=28
|length in=10
|rot dia m=<!-- helicopters -->12.19
|rot number=1
|height m=3.12
|gross weight kg=1018
|eng1 number=1
|eng1 name=Jacobs L-4MA
|eng1 kw=<!-- prop engines -->170
|max speed kmh=201
|range km=322
|ceiling m=4267
}}
==See also==
{{aircontent
<!-- include as many lines are appropriate. additional lines/entries with carriage return. -->
|see also=
|related=
* [[Kayaba Ka-1]]/Ka-2
|similar aircraft=
* [[Avian Gyroplane]]
* [[Buhl A-1 Autogyro]]
* [[Cierva C.30]]
* [[Kellett K-2]]
* [[Pitcairn PA-18]]
|lists=<!-- related lists -->
* [[List of rotorcraft]]
* [[List of military aircraft of the United States]]
}}
==References==
===Notes===
{{Reflist}}
===Bibliography===
* {{cite book |last= Andrade |first= John |title= U.S.Military Aircraft Designations and Serials since 1909|year=1979 |publisher=Midland Counties Publications|isbn= 0-904597-22-9}}
*{{cite magazine|last=Elliot|first=Bryn|title=Bears in the Air: The US Air Police Perspective |magazine=[[Air Enthusiast]]|date=March–April 1997|issue=68|pages=46–51 |issn=0143-5450}} * {{cite book |last= Taylor |first= Michael J. H. |title=Jane's Encyclopedia of Aviation |year=1989 |publisher=Studio Editions |location=London }}
* {{cite book |title= The Illustrated Encyclopedia of Aircraft (Part Work 1982–1985)|publisher= Orbis Publishing}}
==External links==
{{commons category-inline|Kellett KD-1}}
{{Kellett aircraft}}
{{USAAC autogyros}}
{{USAF helicopters}}
{{USAAF observation aircraft}}
[[Category:1930s United States military utility aircraft]]
[[Category:Single-engined tractor autogyros]]
[[Category:Kellett aircraft|KD-1]]
[[Category:Aircraft first flown in 1934]]