"Ken Duffey" wrote in message
...
Kevin Brooks wrote:
"Ken Duffey" wrote in message
...

Andy,



ANDREW ROBERT BREEN wrote:

In article ,
Raoul wrote:


I've had a questions I'd like to foist upon the collective knowledge
here...

I've noticed that their were many planes during the prop-to-jet
transition years from about 45 to about 55 that used counter rotating
propellers. I'm wondering what the perceived advantage was?

Great reply.................

Major snip...................


Not sure whether the Antonev 70 is actually in production yet, but it
uses
four big contraprops..


IIRC, the An-70 is not a contraprop as such - the D-27 engine is a
twin-spool propfan - and the props are driven by the two shafts, not
through a 'normal' contraprop gearbox.

It has 8 blades in the front row and 6 in the rear - 14 blades per
engine - making a staggering total of 56 blades !!!

It is extremely fuel efficient.........


Wait a sec. If this was such an extremely fuel efficient system, the
short-haul airlines would be banging down the various manufacturers'
dorrs demanding such systems--which they decidedly ain't doing. The prop
fan configuration was tested here in the US a few years back (on a DC-9
airframe, IIRC), and it apparently was found wanting (how much of a
problem in that regard the noise issue is I don't know). The An-70 has
had a rather troubled development history (so much so that the Russians
have gotten rather cold to it), and IIRC one of the major problems has
been the powerplant.

Brooks


Ken

Don't shoot the messenger - I'm only quoting what I read .............

From 'Antonov's Heavy Transports -The An-22, An-124/125 and An-70' by
Yefim Gordon, Dmitriy and Sergey Komissarov - No 18 in the 'Red Star'
series.......... purchased yesterday.

"Four ZMKB(Muravchenko) D-27 propfane engines with a takeoff rating of
14,000 ehp and a cruise rating of 6,750 ehp designed by ZMKB Progress at
Zaporozhye. The D-27 is a two-spool engine........

The engines are noted for their high fuel efficiency, the fuel burn in
take-off and cruise mode being 170 g/ehp.h (0.37 lb/ehp.h) and 130 g/ehp.h
(0.29 ib/ehp.h) respectively.........."

I believe they have had not one but two accidents ('95 and '01) tied to the
engines and props?

From Pravda in '99 (not the best source, I'd agree--but it was saying the
same thing the Russian AF folks were saying): "Vladimir Mikhailov says that
the plane cannot be put into production because of its imperfect engine D-27
that is "unsafe, short-life and very expensive." Experts think it is
impossible to get the engine into shape."

english.pravda.ru/main/18/89/357/11829_aviation.html

That does not sound like a ringing endorsement of the powerplants.


I don't profess to know what that all means - I am just posting what I
read.

As far as the dispute between the Ukraine and Russia over the engines -
again, from what I read - this has now been resolved...

From Air Fleet 5/2003 - "In spite of the RusAF top brass's stance on the
An-70 - (to do with structural flaws in the powerplant) -
representatatives of the Russian government believe that the An-70 trials
must be completed 'as sooon as possible'. According to Russian
vice-premier Boris Alyoshin speaking on 15 August - 'there is no reason
for saying that the programme will not be accomplished or Russia is
pulling out of the programme. The commitments Russia made must be met"

"Moscow, 15 June: Russia will allocate about R30m for developing the An-70
military transport aircraft in 2004, Leonid Terentyev, director-general of
the Medium Transport Plane international consortium, told Interfax-Military
News Agency on Tuesday [15 June]. "The Russian side will most likely earmark
about R30m [indicated elsewhere by the same source as being $1 million USD)]
for the An-70 development in 2004. Russia is unlikely to provide more funds
in 2004," Terentyev said. He noted that the upcoming meeting of the
intergovernmental Russian-Ukrainian commission was unlikely to achieve a
radical breakthrough with regards to the An-70 programme."

www.gateway2russia.com/st/art_242733.php

That sounds like anything but a strong endorsement of the An-70 program,
which Russian senior defense officials have repeatedly commented of late as
not being a program they are very interested in pursuing. The Russian Air
Force apparently wants nothing to do with it, preferring its cheaper
Il-76's.

Brooks


Ken