EVERYTHING WAS MANUAL – Bell 47G-5 - FLIGHT 10

For most of us born in the 1950s and 60s the first memory of helicopters on TV was probably on Whirlybirds, a black and white kids show, or when a little older the comedy hit MASH about a field hospital in the Korean War.  The helicopter that was used by both of these shows was the Bell 47G, probably one of the most successful and recognizable aircraft of its time and one from a time before both gas turbine power and automation.  Typified by a bubble cockpit, steel tube structure and two bladed teetering rotor head it was certainly an aircraft I wanted to fly and one which ETPS duly presented to us students whilst on course.

Walking out to the aircraft I was immediately stuck by its three abreast seating and the large(ish) instrument panel set in the middle of the plexiglass dome.  Having got settled into the left hand seat (which in a Bell47 is meant to be the Captains seat) I waited for the instructor to start the large Lycoming Piston six cylinder engine with its vertical direct drive and air cooling.  It was like starting an old car and after some coaxing the engine spluttered into action along with the rotors.  Once warmed up the engine behaved much as any other  Lycoming product and we went through high RRPM and magneto checks to make sure the engine was ready to go.  It probably wasn’t worth thinking about the way all the moving components were on display or the fact that the engine was linked to the main drive of the helicopter through some interesting belt drives.

Once airborne the visibility from the cockpit was truly outstanding and although I had flown the Gazelle a great deal the unobstructed view was truly incredible.  It did however give few references as to the attitude of the aircraft and I did find it a little difficult to maintain the required attitude.  The second and more interesting element was the completely manual throttle system which meant that my left hand had to make changes to the engineer power every time I moved the collective lever.  Having read the flight manual and been briefed on the system I was ready for it but was really unsure how I would cope.  

The good news was that because of the momentum in the rotor head due to the large heavy blades and the way they were balanced rotor rpm changes seemed to occur in slow motion irrespective of whether I had anticipated the required throttle input.  So after a little coaching from the instructor I did start to get used to the system making the required inputs and keeping the RRPM broadly within the required limit (with some clear verbal prompts).  We then took the aircraft out of the circuit at our epic cruise speed of about 70 kts.  With no mechanical or other assistance control inputs were constant but small with the teetering rotor system and balance bar keeping the aircraft vaguely stable as I attempted to fly accurately.

Once finished with the  standard set of manoeuvres that ETPS students use when flying a new aircraft we returned to the airfield to conduct some auto-rotations.  I has always heard that the Bell 47 had great autorotation characteristics but that did not prepare me for the real thing.  The instructor set the aircraft up for his demonstration and then disengaged the rotor from the engine.  The descent was nothing if gentle and everything really felt like it happened in slow motion.    As we approached the ground the aircraft was flared gently and cam to a complete stop before landing and then, much to my surprise the instructor was able to take-off and land again before the rotor speed decayed below the flight limit.

These features are probably why the Bell 47 was such a successful aircraft in both military training and operational roles where such behaviour was kind to students and operational pilots alike.  Additionally, it is always worth noting that , in earlier variants,  the engines were not so reliable and the ability to auto-rotate safely to an engine out landing was essential.

Of course I had my own attempt at the autorotation but without trying the second take-off and landing element.

Flying such old and simple aircraft really helps with understanding the basics of rotor system control and engine governing systems.  The fact that these features still sit so strongly in my mind show how the training worked and perhaps is something we tend to forget when our computerised engine controls do all the work for us.