*125531 was held back on the production line for the incorporation of any

  production type changes.

  Became test a/c with Lycoming T53 engine during 1956 ;

  retired at Bloomfield, CT ;  SOC  -  TT 525 hrs  

From Kaman Report  W-8, dated 15 Oct 1954 , for HOK 125531 : HOK-1 with in length increased tail booms and three 21.3 sq.ft fins  (three fin config. Rev. date 16 July 1954 ; Report S-61)

From Kaman Report W-19 , dated 30 Nov 1954 : The addition of a triangular dorsal and ventral shaped blade, part of the central fin. In this configuration there were three 21.3 sq.ft fins.  

Was seen on a photo of 129803, dated Sep54.  

Contractor’s Demonstartion Tests at NATC, Patuxent River, MD until 16 Dec 1954 

 129810, 129811

After suspension of the BIS tests due to the crash of the NATC 129812 aircraft, various changes were incorporated in the HOK's control systems. For correlation, and consistency of purpose, these test were conducted at Bloomfield using aircraft 125531 which was the original formal demonstration test aircraft.

The BIS tests at NATC resumed on 23 June 1955.

From Kaman Report W-18 , dated 30 Sep 1955 : The addition of a larger dorsal and ventral shaped blade to the central fin. HOK-1  129802 had this configuration on 17 June 1955, when it was damaged due to engine failure (it was destined for the follow on of the BIS trials at NATC).

Kaman Photo 1020  dated 30Aug55 shows the  “bear-paws” installed    (possibly on 125530)

Winterization

The specification to which the U.S. Navy HOK-1 helicopter was originally designed, requires that the helicopter be capable of operating in temperatures ranging from a low of -65 degree F to a high of +120 degree F. The design of the helicopter  took full cognizance of these extreme temperature operating requirements. During development of the HOK-1 helicopter, it was subjected to cold weather tests at the U.S. Air Force Climatic Test Hangar at Eglin AFB, FL. The helicopter experienced no difficulty in successfully demonstrating its suitability for cold weather operations down to -65 degree F.   (Kaman Report R-164, dated 01 Dec 1956)

February 1956 : Start of an engineering development program for structural modifications necessary for the installation and test of the Lycoming XT-53-L-1 gas turbine engine in a bailed HOK-1 helicopter (125531).

This work was performed under contract with the Lycoming Division of AVCO Manufacturing Co., who has developed the XT-53 gas turbine engine under sponsorship of the U.S. Air Force with U.S. Army funds.

One of the other development changes was the extension of the horizontal elevator with 12 inch to each side of the center fin. Done for the benefit of an increase in the static directional stability.

The aircraft was now referred to as HOK-3 and  Kaman Model K-600-3. 

Flight tests in SAR configuration, standard LH hoist, to evaluate water pick-ups. Location :  Lake Congamond, CT  (Kaman Pilot Report 71)

BuAer approval for Removal of Cabin Door Sill Gusset - in all HOK-1 aircraft (Kaman Report R-158)

Canadian Tour , demonstration  to the RCAF at Ottawa  and the RCN at Halifax  (Kaman Memorandum 01 Oct 1956)

27 Sep 1956 first hover and 29 Sep 1956 first flight  of this HOK-1 with Lycoming T-53 engine (now also known as HOK-3 or K-600-3).

A 50-hour ground test program followed, from 01 Oct  to 15 Dec 56. A 60-hour flight test program conducted by Kaman took place from 15 Dec 56 until 01 Mar 57, and Lycoming followed with a program for engine flight test evaluation from 01 Mar 57 up to 01 October 1957, which took place at the Lycoming plant in Stratford, CT.

(Article in “Flight”  26 Apr57 : the Kaman Model K600-4 would have been  a K600-3 with 2 Blackburn Turmo 600 turbines)

HUK-1

HU2K-1

(Seasprite)

15 Feb 1957 marks the start of the HU2K-1 aerodynamic investigation program. Not related to the history written in these website pages, however, the start of the development of a new Kaman helicopter is mentioned here to show the Kaman Corp. efforts for system's innovations and performance. It was for a single main and tail rotor configuration aircraft which was proposed and also submitted in the event that the proposed HOK-3N synchropter configuration might prove to be limited in order to satisfy future NAVY requirements. The HU2K-1 was proposed with a Navy funded GE T-58 engine program, which was expected to satisfy future NAVY helicopter turbine engine requirements (comment by Mr. A.D. Rita)

Proposal for the Kaman K-600-3N turbine powered utility helicopter for the US Navy.

The installation of the lighter, higher powered turbine engine provides significant increases over the established performance of the HOK-1. The greatly enlarged internal cabin space made available by the “external” mounting of the engine, in combination with the substantial power margin, provides a service helicopter of unique capabilities.

The proposed K-600-3N was an advanced helicopter which will : 

--  exploit the extensive growth potential of the HUK-1 with a minimum of design, development, testing and tooling.

--  provide a gas turbine powered utility helicopter for fleet service use in the shortest possible time.

--  utilize a substantial percentage of the logistic support already established for the HUK-1.

--  have a fuselage completely devoted to useful load but which retains the over-all size compactness of the HUK-1.

--  be comprised of components that are either already service tested or whose principles have been developed and refined by this Corporation.

(Kaman Report R-150, dated 02 May 1957)   for drawing click here  

Under BuAer contract the Kaman Corp. started the production of 24 HUK-1 fleet utility helicopters for the US Navy with delivery of the first aircraft in Jan 1958.

by mid 1957 the HUK , HU2K , the XT-53 HOK (K-600-3N) , the H-43A and H-43B programs were under contract.

Under AF contract 33(600)-36190 the Kaman Corp. started the production of 18 H-43A Local Crash Rescue helicopters for the USAF. The initial design of the tail configuration (approved by 02 Apr 1958)  was with two outboard fins (at 15 sq.ft.) and two ventral fins (at 6 sq.ft.) mounted to the end of the booms (no dorsal fins).

The four-fin configuration was introduced , in stead of the HOK three fin, as a benefit to the static directional control requirements.

This tail configuration, including the dorsal fins was tested on HOK 125530 during this time-frame. On 18 Oct 1957 extended outboard fins on the bottom with 4,5 inch were test flown. In this configuration the elevators were extended to 18 inch (each side) in stead of 12 inch (introduced in early 1956 for the HOK-3, and later to the HUK). The outboard fins were also modified with servo-operated rudders on the back side. The directional stability characteristics of the helicopter were vastly improved by this configuration.

Under the same (see here above) AF contract 33(600)-36190 the Kaman Corp. started the development of the  H-43B Local Crash Rescue helicopters for the USAF.  A batch of 20 aircraft for FY58. The initial design of the tail configuration was with two outboard fins (at 15 sq.ft.) and two ventral fins (at 6 sq.ft.) mounted to the end of the booms (no dorsal fins). (The same configuration as for the H-43A).

Hoisting operations from RH side for H-43A program  , with 4-fin tail , ventral only  (Kaman Report R-140C)

129801

Back in 1956 , it was Kaman Aircraft Corporation ’s policy to maintain an active, continuing program of product improvement. The future for growth of the company with helicopter configurations with piston engines was limited.

Kaman already was a leader in the application of turbine power to helicopters. The Kaman Model K-225 was succesfully flown with a gas turbine in Dec51, world’s first helicopter.  In  March 1954 a Kaman HTK-1 (Model 240) was flown powered with two gas turbines. 

Therefor, Kaman initiated the establishment of an  engineering development program with the effort that at the completion of the Lycoming T-53 gas turbine engine development and qualification test phases (1956), the resultant turbine powered test vehicle, now referred to as the HOK-3, was essentially an off-the shelf qualified prototype vehicle ready for production release. The test vehicle selected for the Lycoming test program was HOK-1   BuNo. 125531