Ishimasa Sky Lark EH1 (1980)



 Length  838 mm
 Rotor Head  FP model specific
 Main Rotor Dia   990 mm (Fixed Pitch)
 Engine  2 x Mabuchi 540 (brushed) 9,6V
 Gear Ratio  
 Weight  1600 g 



Sky Lark EH1 Build manual 
For all versions

MacGregor advert from May 1983.


       Brochure for original Ishimasa Sky Lark

Imported by Macgregor in the UK and Germany, the Ishimasa Sky Lark EH-1 proved that an electric helicopter could work with the use of an 'onboard' battery and fly in a similar manner to 'normal' glow engine helicopter.  Limited duration though when using onboard batteries however, with the use of the umbilical cord the helicopter could be powered from a 'car' battery and thus greatly extend its operational time.  The reason for this short flight time was due to a number of factors, overall weight of the helicopter, battery technology and motors used; constructional plastic had not been developed for 'hobby' use so the Skylark's body was made from aluminium like most RC helicopters of that time.  The only electric motors then available were brushed 'buggy' types which were not particularly efficient and so it required two of them to provide enough power; couple this with a speed controller that looked like a bar from an electric fire and efficiency at anything other than full power would have been significantly reduced.  Finally, the technology of the time would only allow the carrying of an 8 cell 1.2 Ah Nicad pack due to their weight as larger capacity batteries would have been too heavy to lift.  When you consider all of the above it must have taken quite a bit of R&D to achieve the balance of body size and thus weight to motor power and battery carrying capability. 

Of note is that the model had an unusual feature for the time, a 'fibre' lightweight tailboom.  Why, well the models balance had to remain constant with battery fitted or without the battery when in tethered mode and the only way to achieve that was to have the battery positioned at the balance point.  Considering the model layout and the desire to give it a semi-scale appearance and not just be a 'pod and boom' machine and the 'constraints' of the battery positioning, a metal boom would have made it impossible to achieve balance under the main mast; neat solution... 


  Jul 1980 UK advert with price   Canadian and US adverts

Sky Lark EH1 Build review  -  Article from a 1980 US magazine by Larry jolly.    

Sky Lark EH1 Build review  -  Article from a 1981 UK magazine Radio Modeller by Jack Barnard.

  • 1981-06 - Skylark body
  • 1981-06 - Skylark complete
  • 1981-06 - Skylark rotor top
  • 1981-06 - Skylark tail
  • EH1-1
  • EH1-2
  • EH1-3
  • EH1-4
  • Ishi01
  • Ishi02
  • Ishi03
  • Ishi04
  • SAM_0187
  • SAM_0234
  • Skylark - LJ side on desk
  • Skylark11
  • Skylark12
  • Skylark13
  • Skylark14
  • Skylark15
  • Skylark16
  • Skylark17
  • Skylark18
  • Skylark20
  • Skylark21
  • Skylark23


Ishimasa Sky Lark EH1 (Bell-Hiller)

Whilst the model was a successful solution to electric flight, because the Sky Lark had limited flying time, a very basic control system and was expensive, it was not bought in any great numbers.  The first point was very firmly governed by technology limitations of the time regarding motor and battery technology and as such very little could be done however, to redress some of the criticism of very basic control, the head was upgraded to a Bell-Hiller system thereby giving a much better response; this was also available as a conversion kit so that an original Sky Lark could be upgraded to the Bell-Hiller control system.  Price? Again manufacturing techniques and the materials involved meant that it was, what it was...

Unfortunately the electric helicopter concept was too ahead of its time and despite the better control still did not sell well and thus was not developed any further so fading away.  However, a few years later the design layout was used, albeit in a more compact form, for the Aisonic Master electric helicopter series.

-  plus - EH1 manual addendum

    Bell - Hiller conversion instructions plus use of locking plate for setting the pitch.  

Two original Sky Larks,  both with Rheostat type speed controller and some period radio gear fitted.  Intend to build one with the radio gear and keep the other as a spare.
Two with Bell-Hiller heads and one in V good condition having been built up as a display model.  Has modern upgraded brushed motors and electronic speed controller along with clamps for fitting an eight cell flight battery plus modern (ish) radio gear and a piezo rate gyro.  Currently having problems keeping the tail drive 'O' belt on the drive pulley because the upgraded motors are deeper so the drive pulley is mounted lower and the angle of pull on the 'O' drive causes it to slip off.  Once I have dealt with this it can be flown.  The second machine is complete and again probably keep for spares.