HOK Design Development Test

 

The content of this webpage is based nearly solely on the contributions received from Mr. Anthony D. Rita ,  please visit this link

 

 

The presentation of the first production model of the helicopter took place on 28 April 1953. Rear Adm. John B. Moss, Navy Bureau of Aeronautics Assistant Chief for Materials and Services, accepted the twin-intermeshing-rotor machine from Charles Kaman, head of the manufacturing company. The following photograph is dated 28 April 1953 :

125528 first acceptance at BradleyFld 28Apr53

 By 03 March 1953 the two 36 inch chord elliptical shaped fins were increased in size to 46 inches (as seen in above photo)

 

 

HOK    AIRCRAFT    BAILED   FOR   ENGINEERING   DEVELOPMENT   and   TEST   FLIGHTS  

   available accepted by BAR R&D left R&D                aircraft history
125528    20 Nov 1952    29 April 1953       1959   left BAR R&D for service with VMO-1 during 1959
125529     Jun 1953  15 July 1953 11 Mar 1954   crashed at Bloomfield, CT ; TT 67 hrs  
125530     Aug 1953  23 Nov 1953 12 Jun 1963   retired at Bloomfield, CT  ; SOC - TT 2001 hrs
125531     Sep 1953    1953 - Nov 1954* 27 Aug 1959

 *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  

129800     Sep 1953  23 Mar 1954 25 Oct 1957   retired at Bloomfield, CT  ;  SOC  -  TT 94 hrs
129801     Oct 1953  09 July 1954 14 Sep 1959   retired at Bloomfield, CT  ;  SOC  -  TT 838 hrs
for individual histories of these 6 aircraft click here   

 

Initially aircraft 125528, 125529, 125530 and 125531 were designated for Kaman's HOK qualification efforts. But because of 125528 's drive shaft failure and crash damage incident on 18 Dec 1953 and the incorporation of the R-1340 engine and other lingering types of developmental problems necessitated adding aircraft 129800 and 129801 to the test effort.  

Aircraft  125531 was held back on the production line for the incorporation of any production type changes which would be dictated by the test efforts. Thereby avoiding non-conforming configuration issues further in the program when 125531 would be introduced for the formal demonstration tests at NATC.

These contractor demonstration tests at Patuxent River, MD would lead up to the Navy 's BIS and FIP test phases in 1955. The concerted preliminary test efforts involving these aircraft were primarily concentrated in the period from the Dec 1953 start to mid July of 1954.

By Sep 1954 a major change in the aircraft's external configuration was established. The increase in the length of the tail booms and the addition of a central dorsal fin assembly consisting of an upper and lower section. 

 

26 June 1950   First contract signed to build 4 HOK aircraft (125528 thru 125531)
20 Nov 1952  125528 Assembly completed and aircraft weighed
27 Nov 1952  125528 First flight or first hover probably before 27Nov , but at last early Dec 1952
     Mar 1953  125528 Kaman Report dated 03 Mar53 : the two 36 inch chord elliptical shaped fins were increased in size to 46 inches
28 April 1953  125528 date of acceptance by the Navy , at Bradley Field, CT
15 Dec 1953  125530 P&W R-1340 engine installed in stead of Continental R-975
 Sep 1954  125531

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)

 Sep 1954  

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.  129816 triangle fin 29Mar55 KamanPh778.JPG

Was seen on a photo of 129803, dated Sep54.  129803 DaytonOH Sep54 MAP photo

19 Nov 1954   125531

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

22 Dec 1954 

 129810, 129811

NATC BIS Tests  starting in Dec 1954. Suspended 16 Jan 1955. Resumed on the 23 June 1955 
 Spring 1955  125531

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.

 Jun 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).

 Aug 1955  

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

 unknown date  

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)

 Feb 1956 - Sep 1956  125531

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. 

05 Jul 1956  125530

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

27 Aug 1956  

BuAer approval for Removal of Cabin Door Sill Gusset - in all HOK-1 aircraft (Kaman Report R-158)HOK 129816 Cabin Door Sill Gusset Mar55.JPG

15 - 27 Sep 1956  125530

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

27 Sep 1956 - 01 Sep 1957  125531

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)

Jan 1957

HUK-1

Following the contractual award from BuAer to built 24 HUK-1 aircraft, a number of meetings were held to discuss the proposed changes to the HOK-1 configuration. In fact only utility mission system changes. One additional change was the horizontal stabilizer design which span was increased. At that time only current on HOK  125531 for the XT-53 Lycoming development program. 
15 Feb 1957

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)

May 1957 K-600-3N

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  

May 1957 HUK-1

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      

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

 

Sep 1957 H-43A

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.

Sep 1957 H-43B

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).

05 Sep 1957  129801

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

15-16 Oct 1957   NATC tests at Bloomfield, CT  with a HOK with a modified tail  (NATC Report AC-4035)
18 Oct 1957  125530 4-fin tail , ventral and dorsal fins    (Kaman Pilot Report 95)

 

 

May 1958 125530 During Air Force FSK trials ; booms with title  “U.S. Air Force”   (photo and  photo-caption)
May-Jun 1958 58-5524 supposed introduction of this H-43A   (formerly a HOK-1)
29 Jul-27 Aug 1958

129801

Flight tests at Bloomfield (Report SMR-474) with H-43A 58-5524 and HOK 129801 (4-fin tail, ventral only) and HOK 125528
11-12 Aug 1958 129801 First flight of proto servo tail , ventral only  (Pilot Report 113)
     1959 125531 with Lycoming T53 seen active flying from Bridgeport Municipal Airport, Stratford, CT  in 1959, with titles on tailblade “US Army - Project - USAF” and “Lycoming T-53” on tailboom ; 4-fin tail configuration
May 1959   Under AF contract 33(600)-37818 the Kaman Corp. started the follow on production of H-43B helicopters for FY59 and FY60. At this moment the initial design of the tail configuration was still valid : 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).

  

 

 

 

HOK KamanReport 15Feb52 W2 p4.JPG

From Kaman Report W-2, dated 15 Feb 1952 :

the initial design of the HOK with a twin tail boom and oval fins (HTK type)

 

 

HOK KamanReport 01Jan53 W6 p4

From Kaman Report W-3, dated 01Jan 1953 :

First tail iteration, from oval type fins to the 36 inch chord elliptical shapped fins - these were increased in size to 46 inches , as reported on 03 March 1953

 

 

HOK KamanReport 15Dec53 W16 p4

From Kaman Report W-16, dated 15 Dec 1953  for HOK-1  125530 :

HOK-1 with increased, 46 inch, tail fins (two)  and P&W R-1340 engine (in stead of the Continental R-975 ; new engine as early as 23Nov53)

 

 

HOK KamanReport 15Oct54 W08 125531

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

 

      

 

W19 Configuration 30Nov54.JPG

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.

However, see here below, seen as early as Sep54    

 

 

 

W18 Configuration 30Sep55.JPG

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 is supposed to be the first aircraft to have received this new configuration in Jun55 and HOK-1 129815 the second one , upon delivery to NATC on 22 Jun 1955. HOK 129810 being the third one by 21 Jul 1955.  

 

 

 

129803 DaytonOH Sep54 MAP photo

HOK-1  129803  photographed at Dayton, OH during Sep 1954 (MAP photo)

This means that the triangular dorsal and ventral shaped blade made part of the central fin as early as this Sep54 date.

 

 

 

129801 20Jan55 photo via SeanCarroll001.JPG

HOK-1  129801 after it roll-over at Bloomfield, CT on 20 Jan 1955 ; the trianglar shaped blades is clearly visible  -   photo via Sean Carroll

 

129816 triangle fin 29Mar55 KamanPh778.JPG

HOK-1  129816 with the addition of a triangular dorsal and ventral shaped blade, part of the central fin. Kaman Photo 778, dated 29 Mar 1955, via AD. Rita



 

HOK KamanReport 30Aug57 W26 139990 thru 140001

From Kaman Report W-26 and W-27 , dated 30 Aug 1957 :

for HOK-1 BuNo. 139990 thru 140001 ; representing the final tail configuration

 

 

HOK ThreeViewDrawing Report R164 01Dec56 1190

HOK ThreeViewDrawing Report R164 01Dec56

 

125530 30Aug55 KamanPh1020 viaNIMH.JPG

HOK-1  125530  30 Aug 1955   - Kaman Photo 1020 , via NIMH


 

 

125531 1956 KamanPh1044 7 viaNIMH.JPG

HOK-1  125531   Mar 1956   - Kaman Photo 1044-7 , via NIMH

 

 

 

138101 Pensacola 14Dec79 bySMiller viaMutza.JPG

OH-43D  138101  VS 3   VMO-2   on display at  NAS Pensacola, FL   14Dec79  -   by S. Miller,  via W. Mutza


 

 

from piston engined Kaman's to the turbine powered  HOK  with a Lycoming T-53 :

 

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 

 

 

 

 

Kaman Report R098 21Mar56 HOK3 P161

Kaman Model K-600-3  , drawing P161 , Report R-098 dated 21 Mar 1956 

 

 

Kaman Report R098 21Mar56 HOK3 P162

Kaman Model K-600-3  , drawing P162 , Report R-098 dated 21 Mar 1956



Kaman Report R102 15Feb56 HOK3

Kaman Model K-600-3  , Report R-102 dated  15 Feb 1956 

 

 

 

 

 

 

Modifications. The fuselage remains unchanged except for the firewall removal, strengthening of certain frames in the center section and rework of the lower pylon area where tail boom loads carry through to the fuselage. The tail support booms are strengthened to carry engine loads and are modified to provide engine support structure.

The horizontal stabilizer span became 100 inches, versus that of 84 inches for the HOK-1.

The upper half of the center tail fin is slightly reduced in area (now 7.14 sq.ft) and is constructed of fire-proof material, titanium, in stead of the light metal alloy structure originally used. The exhaust duct is a short, stainless steel pipe with a slight upward curvature.

 

 

125531 T53engine Mar56 Report R098 8

HOK-3  125531 with T53 engine, Bloomfield, CT  Mar 1956 - Kaman Report R-098

 

 

125531 T53engine Mar56 Report R098 9

HOK-3  125531 with T53 engine, Bloomfield, CT  Mar 1956 - Kaman Report R-098

 

 

125531 T53 KamanPh1044 7 NIMilHist

HOK-3  125531 with T53 engine, Bloomfield, CT  Mar 1956  -  Kaman Photo 1044-7 , via NIMilHist

 

 

125531 022 Lycoming byFrankGuaitis EBay2014 

HOK-1 125531 with extensively modified center blade , needed for protection against the heat from the Lycoming T-53 engine ; photo copied from an EBay2014 auction, photo credit Frank Guaitis

 

125531 T53 Bridgeport 1959 KenCollinge Internet

HOK-1 125531 with Lycoming T-53 engine and the 4-fin tail , note the exhaust pipe of the Lycoming T-53 engine ; photo by Ken collinge taken from Internet, photo location Bridgeport, CT during 1959 

 

 

HOK ThreeViewDrawing Report R164 01Dec56 1190

HOK-1  Three View Drawing  - Kaman Report R-164  01 Dec 1956

H43B DRAWING Kaman Report R193B 05Sep57

H43B with initial tail configuration : only ventral fins attached to the boom -  Kaman Report R-193B  05 Sep 1957

 

 

last update 13/02/2017