[skanchan95]

Originally Posted by Ricci

It's 108 sqd not 101, the one that's been reinstated to get the Rafales, right? Haven't tallied with BR but wikipidia shows Pathankot.

No, it is 101 Sqdn "Falcons" who will be the second Rafale Squadron. Although I admit I wrote 108 Sqdn in my earlier post by mistake.

Quoting from this article which states 101 Sqdn on Rafales will be based at Hasimara.

The IAF also plans to resurrect another former MiG-21 squadron, 101 Squadron or the “Falcons”, which too was “number-plated” (removed from the active list, and its identity mothballed for future use) some years ago when its MiGs become too old to fly. 101 Squadron, the second Rafale squadron, will be based in Hashimara to operate on the Sino-Indian front.

Both squadrons - No. 101 "Falcons" & No. 108 "Hawkeyes" were MiG-21M squadrons and it is easy to get confused between the two. No. 17 Sqdn "Golden Arrows", which is the first IAF Rafale squadron, too was a MiG-21M squadron before it was numberplated in 2011 at Bhatinda AFS.

101 Sqdn was numberplated in 2012 when based at Naliya AFS.

No 108 Squadron, based at Nal AFS, was one of two remaining MiG-21M squadron when its numberplating was announced in 2018, the other being No 35 Sqdn "Rapiers"(who may still be flying specially modified MiG-21Ms in the EW role). No. 108 Sqdn was the first of two IAF Squadrons to receive first of the 48 direct supply MiG-21MFs in 1973(the other being No. 7 Sqdn "Battle Axes"), before converting to HAL-built MiG-21Ms in later years. 108 Sqdn later traded their MiG-21Ms with MiG-21MFs of No. 7 Sqdn.

[DrPriyankT]

Originally Posted by Ricci

It's 108 sqd not 101, the one that's been reinstated to get the Rafales, right? Haven't tallied with BR but wikipidia shows Pathankot.


That's likely not much of a factor. Twin engine planes can start up and taxi on one engine, while spooling up the other engine by the time they reach the runway threshold. Unless your jet is sitting ready on the ORP situated right by the threshold, a single engine isn't going to give much of a headstart.

Yes, usually new jets are better off based deep inland where the IAF can get familiar with them with less tapping (electronics/signals gathers, radar tracks for guessing kinematic performance) from neighbours.

Sir, I feel, like all aircraft, the deep testing will be done at TACDE Gwalior, where it will also be used for DACT against Su-30's, LCA, Mig 29 and Mirage 2000. There, the electronics can be tested fully away from prying sensors of our neighbours. Similar testing can also be done at ATSE Bangalore.

[avishar]

This is the most scathing account of HAL that I think has ever come out. It is about the Dhruv, particularly it's eligibility for the Naval Utility Helicopter program which the government wants to procure via the Strategic Procurement model, where an Indian Pvt manufacturer (not HAL) ties with an MNC to make the product in India for the Navy. The program can actually be traced back to the late 70s when the Navy wanted to start replacing their Chetaks and one of the reasons for the existence of the Dhruv.

https://www.livefistdefence.com/2020...commander.html

The Truth Hurts, Says Indian Navy’s 1st Dhruv Flight Commander

Well before we embarked the carrier, we had to contend with many other issues. The strangest one was that whenever it rained, it poured inside the cockpit. Water would come through the overhead CB panel, and pour on the collective pitch where the engine control was located. Water would drip on the instrument panel. Water would drip on the passenger seats. I remember the AME of the civilian Dhruv telling me that the ONGC Chairman when flying on board the civilian ALH once had to use a newspaper to shield himself from rain. HAL will again claim that this point has been addressed. But the main issue again begs question, why was this not checked out in design and before delivery?

....


During acceptances at HAL, we would find that individual components would have been switched from other helicopters. In other words, the log card would state that for eg, the fuel pump serial no 12345 was installed, but the actual item on the aircraft would be serial no 98765. Once we realised this, then it became de-rigueur to physically inspect each and every component to check that the component is correct. HAL were concerned about this, and would say, why are you so fussy? Why is this so important, you may ask. It’s important because each component has certain flying hours and a defect history that is recorded in the log card, and ensures that nothing which is defective or with more flying hours on it than recorded is installed. Would you ever think of doing something like this from any foreign vendor? One expects a certain level of integrity and honesty from any vendor, especially a PSU that is supposed to be trustworthy.

The Final assembly line of the helicopter used to be very bad. There was no proper hygiene maintained. For eg, all the metal filings from the drilled holes would fall to the aircraft floor, never to be cleared. There was no template being used for the drilling of holes, so each panel had to be hand-crafted because there was nothing standardised. I have personally seen people working on the open Main Gearbox / IDS with tools and pens sticking out of pockets. Anything could fall out of the pocket into the gearbox, causing dents and leakages. We have removed ballpoint pens and nuts / bolts under the floor board, in the area of the floatation gear bottles after hours of flying. A very dangerous incident was when we had sparking and melting of the alternator cables. Never heard of. The HAL solution was to replace the cables. All was well, and the team that had come with the cable, told our engineer, that the cable was too long, and they wanted to use tiewraps (or tie-wire) to secure it. Fortunately for us, the designer also came by that day to find out what was wrong. He was horrified to find that the persons installing the new cable did not have a wiring diagram, and had routed the cables incorrectly.

The article is a result of a rare but public war of words going on between HAL and Indian Navy over NUH.

[navin]

Originally Posted by Jeroen

Think classic Royal Enfield thump, but airborne.

The Youtube video don't do it justice

Originally Posted by skanchan95

Some were even modified to be used as a gunship in the Vietnam War by the US Army

That thump is not a very useful feature during wartime. The Vietcong could hear the UH-1 and CH-47 coming from miles away and melt away.

https://www.youtube.com/watch?v=i8qF0JorXaM

Eventually, the US Armed Forces looked at ways to reduce that "thump"

One option considered was a "self-feathering rotor". This not only reduced the thump but also made helicopter rotors more efficient.

See the links below.
https://ntrs.nasa.gov/archive/nasa/c...9870005742.pdf
https://pdfs.semanticscholar.org/2fd...fa6dd7463f.pdf
https://scholarsmine.mst.edu/cgi/vie...masters_theses
and the "References" in the link below
https://link.springer.com/chapter/10...-319-24768-7_1

[Jeroen]

Originally Posted by navin

See the links below.

Interesting to see a Thesis from 1949!!

All done on a type writer with some neat little drawings. No word processors in those days.

I did my thesis in 1979-80. I was lucky as my parents bought me an electrical type writer, which was pretty high tech stuff at the time.

Still it was a pain if you discovered big mistakes in parts typed out already. Sometime you ended up redoing pages after pages, just to accommodate an extra paragraph.

A lot of work has been done of the sound of helicopters, but it is still very easily recognisable and you can always hear them come from far away.

The Chinook has a very specific thump. Having two rotors must make it more difficult as you have the same challenges twice. (double number of blades, double number of blades passing over the fuselage etc etc)

Not sure if dual rotor helicopters have some sort of synchronisation between engines/rotors? Akin to how we used to have on the large prop-driven planes?

Jeroen

[Foxbat]

Originally Posted by navin

That thump is not a very useful feature during wartime. The Vietcong could hear the UH-1 and CH-47 coming from miles away and melt away.

Thats a very relevant point you make and helps explain this statistic:

According to research by The Vietnam Helicopter Pilots Association there were about 11,827 helicopters that served in the Vietnam War, out of which 5,086 were destroyed.

Thats a 43% loss rate!

Source: http://www.ww2wrecks.com/portfolio/5...e-vietnam-war/

[navin]

Originally Posted by Jeroen

I did my thesis in 1979-80. I was lucky as my parents bought me an electrical typewriter, which was pretty high tech stuff at the time... Sometimes you ended up redoing pages after pages, just to accommodate an extra paragraph.

OT: I feel your pain. I wrote my thesis using an IBM Selectric. It had a "Ball" that would "spin and hit" depending on the letter you required. You could even change the font by changing the "Ball".

[Jeroen]

Originally Posted by navin

OT: I feel your pain. I wrote my thesis using an IBM Selectric. It had a Ball that would "spin and hit" depending on the letter you required.

You were lucky, very cool!

Going seriously off topic here but I do remember those well. My dad’s secretary was one of the very fist users of these. I remember our dad taking us all to see it at his office. We were absolutely fascinated! It was so out of this world for us. Having grown up with mechanical type writers.

IBM had made these massive posters of these balls. about 1 meter in diameter, they looked like some sort of spooky alien spaceship!! Had one on my bed room wall for some years!

https://nl.m.wikipedia.org/wiki/Best...c_typeball.jpg

[V.Narayan]

Originally Posted by Jeroen

Not sure if dual rotor helicopters have some sort of synchronisation between engines/rotors? Akin to how we used to have on the large prop-driven planes?

The rotors of a twin rotor helicopter synchornize automatically as both are driven off the same gearbox. True for the Kamaov's as for the Chinook. In the Chinook the risk of rotor collision is obvious. in Kamov's with their co-axial layout the risk of rotor collision is in the vertical plane.

Originally Posted by Foxbat

According to research by The Vietnam Helicopter Pilots Association there were about 11,827 helicopters that served in the Vietnam War, out of which 5,086 were destroyed.

Thats a 43% loss rate!

Good for the North Vietnamese. Fighting a war of independence that USA had absolutely no business getting involved in. Little known fact. When in 1954 Ho Chi Minh had routed the French a peace accord was signed that temporarily split the country at the 17th parallel with the agreement that USA, China, USSR and UNO will work to hold elections across the country. India chaired the International Control Commission with Canada and Poland as the working members to implement the peace & the elections. USA knew that Ho Chi Minh would win hands down across the entire country while their candidate Diem stood know chance. They then avoided the elections altogether by not signing the accord at the nth moment after all other parties including the French had agreed to sign!!!! Talk of perfidy. Who knows what course history would have taken had those elections been held.

PS: Don't mean to offend anyone who is pro-American with regard to the Vietnam war.

[Sutripta]

Originally Posted by Foxbat

Thats a 43% loss rate!

Let alone under enemy fire conditions, helicopters have never been the most reliable of flying machines.

Originally Posted by navin

OT: I feel your pain. I wrote my thesis using an IBM Selectric. It had a "Ball" that would "spin and hit" depending on the letter you required. You could even change the font by changing the "Ball".

Always wondered how that ball was manufactured in commercial quantities and prices.

Sutripta

[ads11]

Originally Posted by Jeroen

I did my thesis in 1979-80. I was lucky as my parents bought me an electrical type writer, which was pretty high tech stuff at the time.
Still it was a pain if you discovered big mistakes in parts typed out already. Sometime you ended up redoing pages after pages, just to accommodate an extra paragraph.

Considering I'm currently writing up my PhD thesis now this was interesting to read about. Sure makes me realise how much easier I have it in the sense a lot of the hassle with editing and referencing compared to your day (my dad never ceases to remind me whenever I would gripe)!

Originally Posted by V.Narayan

Good for the North Vietnamese. Fighting a war of independence that USA had absolutely no business getting involved in.

Again going off topic but I would Highly recommend watching Ken Burns Vietnam War documentary! I believe it should be available on Netflix. The Vietnam War was one conflict I didn't really know much about and this 10 part series was absolutely magisterial in scope. It covered a lot of ground and had veterans from all sides, US, North Vietnamese and South Vietnamese providing their insight. It's harrowing to watch but I would thoroughly recommend it. In fact it was the first Ken Burns series I watched, the man has an extensive body of work covering the US Civil War, The Roosevelts and WW2 to name a few.

Coming back to the topic, the distinctive rotor thump of the Huey was absolutely a giveaway. It's why the Russians and Chinese were so keen to inspect whatever intact wreckage (think it was mostly the tail boom) of the scuttled "stealth" Black Hawk that was used to insert the Navy SEALs when they killed Bin Laden. Starting from the cancelled Comanche programme, the US military in particular has been extremely interested in ways to reduce the audible sound signature and you've seen some of those features make their way outside the classified realm. Just looking at the rotorcraft operated by SOAR, the most elite rotary unit in the US military you see that not only are the engine intakes and outlets baffled to reduce sound and heat signature, I think the rotor blades themselves have unique treatments on the leading edges, all with the goal of reducing that signature.

Originally Posted by avishar

This is the most scathing account of HAL that I think has ever come out.

Glad to see someone bring this up. I've been following it a bit on Twitter where it all seems to have kicked off with comments made by Retd Adm. Arun Prakash. Now some people shortened his longer statement on the matter and obviously in doing so it came across as scathing, and that triggered some in the HAL camp. Overall though having seen the interview, and considering the fact that as a distinguished IN aviator himself, Adm Prakash is absolutely coming from a place of truth with the valid criticisms he brought forward regarding HAL. HAL absolutely has an issue with not being able to say no to anything, they'll say yes to whatever is asked of them, even if it's ludicrous to assume they can achieve the goal and what unfortunately happens is achievable targets and programmes get waylaid in their haste to try and do all this other stuff. Personally I find this overpromise and under deliver aspect of HAL absolutely infuriating because it frustrates me that they're handicapping themselves by their inability to be pragmatic and/or realistic about their own in house capabilities. Naval rotary wing aviation is absolutely handicapped considering how few platforms we have for the many surface vessels and end use scenarios we need it for. Such a shame considering how well indigenous naval shipbuilding has done..

Here's the interview for anyone interested:

https://www.youtube.com/watch?v=cKCI...ture=emb_title

Comments in question are around the 22:40 mark

[Sutripta]

Originally Posted by Jeroen

The Chinook has a very specific thump. Having two rotors must make it more difficult as you have the same challenges twice. (double number of blades, double number of blades passing over the fuselage etc etc)

But no tail rotor. Which I believe is a major contributor to the signature chopper sound.

Not sure if dual rotor helicopters have some sort of synchronisation between engines/rotors? Akin to how we used to have on the large prop-driven planes?

Which planes? Unless you mean contrarotating props?

Sutripta

[Jeroen]

Originally Posted by Sutripta

B
Which planes? Unless you mean contrarotating props?

Essentially all multi-engine prop planes.

When these multiple propellor don’t turn in synch there is a noticeable beat of the engines noticeable, noise and vibration. So the props RPM and or pitch get adjusted, so they fall in sync.

On the earlier big props, it was the flight engineer’s job. Once the plane was properly established in cruise he would tweak the engine control accordingly. On more modern prop plane there are actual electronic prop synchronisers.

https://en.wikipedia.org/wiki/Propeller_synchronization

Pilots used to rate their Flight Engineer skills by how quickly and how well they could get the engines to synch and keep them in sync!

The very same applies to twin engine / twin propellor boats. Many modern twin engine control system tend to come with some form of auto-synch button/feature.

Here is quite the fancy system:

https://www.glendinningprods.com/products/synchronizer/

or you get yourself one of these cool Synchronizer gaugers and adjust manually:

https://www.greatlakesskipper.com/bo...s/synchronizer


Jeroen

[Sutripta]

^^^
So almost like syncing generators.

Does the ATR have this? Because it has an annoying thrum. (The Dash does not.)

Sutripta

[navin]

Originally Posted by V.Narayan

PS: Don't mean to offend anyone who is pro-American with regard to the Vietnam war.

The people I feel for are the "kids" they sent to fight. Most were unprepared physically, psychologically, or intellectually.

Originally Posted by ads11

Again going off topic but I would Highly recommend watching Ken Burns Vietnam War documentary!

Coming back to the topic, the distinctive rotor thump of the Huey was absolutely a giveaway. Just looking at the rotorcraft operated by SOAR, the rotor blades themselves have unique treatments on the leading edges, all with the goal of reducing that signature.

Yes, the Ken Burns Documentary is very interesting. Seen it at least twice.

I believe the "unique treatment" to the leading edges is now in the public domain. I know the Clinton Administration had initiated some program to transfer some of that stealth technology to the Chinese.

Clinton was really Pro China. He even pushed for their inclusion into the WTO and giving them MFN status.