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Helicopter upgrade

For a number of years, a set of works was performed in accordance with the joint decisions of the industry with participation of all concerned enterprises and organizations.

As a result of improvements in reliability, bearing capacity as well as service life of tail transmission of helicopters Mi-8MTV, Mi-171, Mi-171E, Mi-8AMT and their modifications, to replace the standard tail transmission 8A-1500-000, the modified transmission 8M-1500-000 was developed and launched in batch production, which has a number of significant advantages compared with the standard one.

The producer of assemblies of modified tail transmission (AMHT) is JSC Reductor PM.

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Name and designation of aggregates of the modified tail transmission (AMTT):

  • intermediate gearbox 8М-1515-000;
  • tail shaft 8М-1516-000;
  • tail gearbox 8М-1517-000.

 

These aggregates units are interchangeable* with tail transmission aggregates No.8A-1500-000 both by set, and by elements according to bulletins** and Developer letter*, but in comparison with a standard transmission, they have enhanced durabillty and a number of construction and operational advantages. Aggregates of the modified tail transmission (AMTT) Upgraded units are designed to operate instead of the previously developed tail transmission aggregates (TTA – 8А-1500-000):

 

  • intermediate gearbox 8А-1515-000;
  • tail shaft 8А-1516-000;
  • tail gearbox 246-1517-000.

 

 

I. The main advantages of the upgraded transmission units:

 

 

1. Intermediate gearbox 8М-1515-000.

Grinding of gear teeth of the upgraded intermediate gear 8M-1515-000 (unlike the 8A-1515-000) has increased the strength margin by 1.72 times at the bending and by 1.35 times on the contact, and the use of heavy duty bearings allowed to increase their durability from 1.18 to 3.74 times (in comparison with No.8A-1515-000), which leads to an increase of durabillity.

 

2. Upgraded tail shaft 8М-1516-000.

In the upgraded parts of the tail shaft including pipes and splined couplings, the pipe of enlarged diameter and couplings using splines with profiles are applied, thus increasing the contact area and reducing the bearing stress. In addition, the amount of grease in the spline coupling is increased by 1.5 times.

3. Upgraded tail gearbox 8М-1517-000.

In the upgraded gearbox, bevel gears with circular spiral tooth are applied. Similarly the intermediate gearbox, grinding of gear teeth of the upgraded gear has increased the strength margin by 1.71 times at the flexural and by 1.34 times on the contact, and the use of heavy duty bearings allowed to increase their durability from 1.17 to 2.2 times.

Upgraded tail transmission units for Ми-8МТВ, Ми-8АМТ helicopters and their modifications provide as follows:

  • increase the transmission capacity up to 1050 hp (instead of 900 hp for the transmission No.8A-1500-000);
  • gear operation with a mixture of 50% ТСгип oil and 50% АМГ-10 oil, with Б-ЗВ oil and Turbonycoil-98 oil compared with only mixture of 50% ТСгип oil and 50% АМГ-10 oil in the transmission units No.8A-1500-000.

 

Resource indicators of tail transmission aggregates for helicopters of Mi-8/Mi-17 family

 

  Tail shaft Intermediate gearbox Tail gearbox
Helicopters Established metric *** 8А-1516-000 8М-1516-000 8А-1515-000 8М-1515-000 246­-1517-000 8М-1517-000
Mi-8МТВ-1, Mi-8АМТ Р1Р/1РСС 2000/10 3000/14 2000/10 3000/15 2000/10 3000/15
MРР/МРСС 2000/8 3000/14 2000/8 3000/15 2000/8 3000/15
НР/НСС 6000/- 12000/- 6000/- 12000/- 6000/- 12000/-
Mi-171 Р1Р/1РСС 2000/10 3000/14 2000/10 3000/15 2000/10 3000/15
MРР/МРСС 2000/8 3000/14 2000/8 3000/15 2000/8 3000/15
НР/НСС 6000/- 12000/- 6000/- 12000/- 6000/- 12000/-
Mi-17-1В Р1Р/1РСС 1500/9 3000/14 1500/9 3000/15 1500/9 3000/15
MРР/МРСС 1500/6 3000/14 1500/6 3000/15 1500/6 3000/15
НР/НСС 3000/- 12000/- 3000/- 12000/- 3000/- 12000/-
Mi-171Е Р1Р/1РСС 2000/10 3000/14 2000/10 3000/15 2000/10 3000/15
MРР/МРСС 2000/8 3000/14 2000/8 3000/15 2000/8 3000/15
НР/НСС 6000/- 12000/- 6000/- 12000/- 6000/- 12000/-
Mi-17В-5 Р1Р/1РСС 1500/9 3000/14 1500/9 3000/15 1500/9 3000/15
MРР/МРСС 1500/6 3000/14 1500/6 3000/15 1500/6 3000/15
НР/НСС 3000/- 12000/- 3000/- 12000/- 3000/- 12000/-

***
Р1Р – resource until the first overhaul, hours;
1РСС – service life limit until the first overhaul, years;
МРР – time between overhauls, hours;
МРСС – time between overhauls, years;
НР – service life limit, hours;
НСС – assigned service life limit, years.

 

II. AMTT operational features

 

The aggregates of the modified tail transmission are able to operate and function normally within the specified resource and the life time on land and in-flight in the operating modes ranging in different climatic conditions, including marine and tropical environment, with relative humidity up to 100% at a temperature of up to plus 35° С. The aggregates can be operated at ambient temperatures between minus 60 and plus 50° С, and at altitudes up to 6500 meters above sea level. They meet the requirements of the АП-29, FAR-29.

Mounting and dismounting of the aggregates of the modified tail transmission of the helicopter tail transmissions can be carried out by personnel of operating organizations according to the «Helicopter maintenance manual» taking into account the bulletins with code БУ-Г, БУ-АБ.

 

III. Additional information

 

Helicopter weight changes by + 9.475kg.
Helicopter center-of-gravity position changed by 9mm aft.
Resources and life time of the helicopter and its systems when installing AMTT are unchanged.

* Interchangeability of AMTT with aggregates of standard tail transmissin confirmed by mail of the developer (Mil Moscow Helicopter Plant, JSC) ref.No.13267/8 dated 29.12.2015 and the letter of the manufacturer (Reductor-PM, OJSC) of the upgraded transmission ref.No.275-41 /ref.No.5610 of 06.07.2015.

 

The upgraded intermediate gearbox No.8M-1515-000 is fully interchangeable with the intermediate gear No.8A-1515-000.

Upgraded tail shaft No.8M-1516-000 is fully interchangeable with the tail shaft No.8A-1516-000, however, the installation of the tail shaft No.8A-1516-000 in conjunction with upgraded intermediate gearbox No.8M-1515-000 and tail gearbox No.8M-1517-000 is not allowed.

Upgraded tail gearbox No.8M-1517-000 is fully interchangeable with tail gearbox No.246-1517-000 in place of joint with tail rotor and controls.

At the tail gearbox to fuselage joint, interchangeability is partial:
two bolts securing the gearbox No.8M-1517-000 are replaced with studs on which the self-locking nuts are installed, and the bracket mounting textolite guides of the directional control chain is replaced.

** Current bulletins on helicopter upgrades:

  • Information bulletin: № 8М036;
  • Mi-8АМТ: № АМТ3096-БУ-Г и № АМТ3096-БУ-АБ;
  • Mi-171, Ми-171Е: № АМТ3096-БУ-Г and № АМТ3096-БУ-АБ;
  • Mi-8МТВ-1: № Т3033-БУ-Г;
  • Mi-17-1В, Mi-17В-5: № Т3528-БУ-АБ, № Т3529-БЭ-АБ.