When we first began selling MTV propellers for Russian aircraft some 25-years ago, there was only one available propeller, the MTV-3-250. Since then, and to a large extent as a result of our suggestions, the situation is more complex with more choice for customers, and inevitably with more difficulties in ordering, and from our point of view in stocking!
An MT propeller is designated along these lines : MTV–9–B–C/CL/250–27
MTV – made by MT and variable pitch/ –9 is the hub type / –B is the attachment flange/ C/CL is the hub operating mechanism/ 250 is the propeller diameter in cms/ 27 is the blade profile
To examine these separately:
- The MTV-3 utilised a McCauley hub, modified by MT with MT wood/composite blades. By virtue of the McCauley hub it was heavier than the more recent MTV-9, and has also been the subject of a major AD. However this propeller has not been produced for over 10 years, and any prop being ordered today will be an MTV-9.
- The MTV-9 is an all MT design; with an MT lightweight hub designed specifically for aerobatics.
- MTV-3s and earlier MTV-9s operate at a higher oil pressure than the Russian V-530 propeller. If, therefore, you are replacing a V-530 with one of these earlier propellers you need to increase the oil pressure by changing the oil pressure control springs, which we can supply.
- For the last 9 years, all MTV-9 propellers operate at the same oil pressure as the Russian V-530. However many pilots prefer to increase the oil pressure, since this does result in a more positive and quick pitch change, obviously important in aerobatics.
- MTV-3 and MTV-9 propellers were originally only available with a ‘Western’ (i.e. SAE) flange. This meant that the propellers had to be fitted with an adapter to fit onto the radially-splined Russian hub. This added some weight directly at the nose of the aircraft. Also it made the propeller a little more difficult to balance dynamically. Structurally however this fitting seemed very strong.
- At our suggestion, Vedeneyev then made a Western flange to fit onto the high performance (typically 400-hp) engine, which could then accommodate the MT propeller directly. The ‘B’ is therefore the ‘Western’ flange on the propeller.
- We encouraged MT to develop a new flange that would go directly onto the Russian hub without the need for an adapter. This was done some 15-years ago, and this is the ‘K’ flange.
- Since all MT propellers are handmade, the diameter can be chosen. As a principle a smaller diameter increases speed, but a larger one provides greater acceleration and rate of climb(obviously important for aerobatics), but at a slight cost in speed. Generally our advice would be to have the largest diameter prop that the aircraft can take, since apart from anything else the M14P engine is geared and therefore tip speeds remain relatively low.
- The MTV-9 is made in diameters ranging from 200cm, but for production and certificated propellers the maximum is 260cm. Larger diameters, indeed up to 290cm can be manufactured, but only on an individual application basis and not in terms of standard production.
- The diameter of the V530 propeller is 240cm, and we recommend an MTV-9 250cm for Yak-18T and Yak-52. We do not consider it prudent to use a 260cm blade, simply for reasons of ground clearance. However some owners have used this successfully. Our own recommendation is that if the oleos and tyres are hard, and the aircraft is always operated off hard runways it would be fine. If not, then these aircraft should have a 250cm blade.
All Sukhois and Yak-50 can accommodate the 260cm. Some Yak-55s tend to have undercarriages that ‘sag’ and therefore can have clearance problems with the 260cm.
- The –27 blade profile is the one that has been historically used. When we asked MT to develop a new propeller for the 450-hp engines, but retaining the 260cm diameter, they introduced the –29 ‘wide-chord’ blade. However we found that in properly conducted back-to-back tests the –29 profile gave between 2% and 12% enhanced performance (dependent on flight regime). For this reason we typically only sell –29 blades.
A further complication is that MT now offer small and large spinners.
We sell about two large spinners for each small spinner, and although the reasons for choice are often purely aesthetic, we have found that the larger spinner gives slightly better engine cooling, due to better airflow.
We would also point out that although spinners and propellers are priced separately, after manufacture it is difficult to change, since the primary balancing for the propeller is attached to the spinner back-plate during manufacture.
Governors: MT produce an excellent lightweight governor, which saves approximately 0.75 kilograms (2lb), and is specifically designed for aerobatics, being very quick-acting in pitch-change.
Special Colours: The standard colour of an MT propeller is white with red tips, but any other colour combination can be organised.