Cabin noise levels in old airliners

[JKerman]

I was wondering if anyone knows what the noise levels in old airplane cabins (e.g. Tri-motor, Boeing 247, Constellation, De Havilland Comet, Boeing, 707) were, in decibels. I've searched the internet and can't find any information on this.

[evansb]

You are in for quite a chase. Douglas was one of the first aircraft manufacturers to do extensive acoustic testing of cabins in the late 1930's and early 1940's. Douglas lead the way by stuffing sound deadening material into the hollow aluminum tubing of passenger seats. Subjective noise levels will vary, of course. Vibration accompanying a loud sound will always make the subject think the sound is louder than it actually is. In the late 1940's and early 1950's, several Trans-Atlantic low-cost operators routinely removed the sound deadening materials from Constellations and DC-4's to increase payload at the price of their passengers damaged ear drums. The good ole days weren't always that good. Nostalgia ain't what it used to be.

[vapilot2004]

Accurate noise measurements can be informative, although to truly appreciate the difference between jet powered flight and piston powered aircraft, vibration needs to be considered as well. The difference between the two is nothing short of dramatic.

My family belonged to a flying club and as a child I got to experience a few trips in a Martin 404 and an L749 Connie. The vibration was exciting and noise tremendous on both aircraft. We would have to raise our voices almost to a yell in order to be heard across the aisle on the Constellation. I would guess the difference must have surely been north of 20db at cruise.

[ZFT]

I was wondering if anyone knows what the noise levels in old airplane cabins (e.g. Tri-motor, Boeing 247, Constellation, De Havilland Comet, Boeing, 707) were, in decibels. I've searched the internet and can't find any information on this.

Maybe memory dulling with age but I recall both Britannia and VC10 being quite quiet. B727 too.

[Heathrow Harry]

Hmm

as I remember it 727-707 -737/757/767-747-Tristar/DC-10 -777-A380 in general terms of decreasing cabin noise

The 111 was a bit noisy near the back as was the Trident and the Tu-154 but the DC-9 seemed quieter than the 111 all round

Anything with propellors was MUCH noisier but less vibration in a turboprop

[DaveReidUK]

Anything with propellors was MUCH noisier but less vibration in a turboprop

Though the Vanguard made a valiant effort, lovingly known as the Vickers Vibrator to regular passengers.

[rog747]

707-320C was very quiet - on approach to LGW from Palma 1969 on a Cale 707 i thought the engines had conked out

[vctenderness]

The advertising tag line for the VC10 was “Slip across on the quite”. From my memory it was, on the inside, far quieter than the 707 however on the outside it was a different story altogether!

[GROUNDHOG]

I recall an epic flight in a BEA Vanguard Gibraltar to Gatwick, if I remember it took nearly five hours because of the winds and at the end of it I was nearly deaf, the noise and vibration were dreadful. Good job it was the sixties because none of us noticed much back then anyway!:ok:

[brakedwell]

The Britannia first class section was normally at the back end of the aircraft due to noise and vibration, which was loudest in line with the props. It was remarkably quiet in the rear cabin, spoilt only by a bit of wind noise..

[Heathrow Harry]

should have gone easy on the Baked Beans & Lager..............

[RedhillPhil]

Memories of coming home after three and a half years in Malta on an Eagle Airways DC-6 are of continuous up and down noise plus vibration. Our seats were over the wing.

[lsd]

Cannot recall noise levels but as a young boy remember getting off BOAC Argonauts and Stratocruiers used on the West Africa routes and wondering why my teeth were loose in my gums - going to sleep with my head resting on the window/fuselage..?

[Alan Baker]

Never flew in a piston airliner, but judging from movies of the time they were all whisper quiet on the inside and as smooth as silk!!!

[ian16th]

The Blackburn Beverley's of RAF Transport Command were not very quiet at all.

[pax britanica]

Not tried the 78 or A350 but the A 380 is extremely quiet

Back in the day tho rear engine jets were quiet on the inside but on the outside whoa.... A VC10 sounded like a whole squadron of Phantoms and made everything around you that could vibrate vibrate. And Caravelles could still be heard while they were miles away in the climb out

The 707 320C was quiet at flight idle in the descent but outside with gear and flaps down it emitted a piercing scream for the last few miles down the LHR glidepaths one of which passed right over a Cinema in Hounslow I used to frequent as a kid and seemed just as loud as standing in the street outside.

The MD80 series were the best balance of in and out noise for the rear engine generation although at the end off their careers the oddly nicknamed Mad Dogs were the noisiest when mixed in with the Minibuses and later 737s. Fantastic to fly in up front though with no engine noise at all and absolutely one of my favourites to fly on.

I never flew on a recip prop but living close to LHR back when the SW/NE runways in use there was a big variation in engine noise, I would say the powerful turbo compound engines on DC7Cs were quiet , DC6s didnt seem to be working their engines all that hard ( probably why they outlived all the others) Noisiest were Argonauts and Yorks with their snarling Merlins , the US radials were definitely much quieter.

A lot safer, faster, smoother and quieter today but back then spotting or just a keen interest saw a wonderful variety of types pass through LHR.

[Rosevidney1]

The noisiest civilian flight that I can recall was in an Argonaut of Air Links from Germany. One of the worst landings followed!!!!

[Heathrow Harry]

The Blackburn Beverley's of RAF Transport Command were not very quiet at all.


A mate of mine (a Scout) came back from Oman in one - said it took forever and was an experience not to be repeated at any cost

[goudie]

The RAF Hastings was very noisy and uncomfortable. The first time I flew in one, on take off, sounded as if all the ‘big-end’ bearings had gone! In comparison a Comet was extremely smooth and quiet.

[RatherBeFlying]

In the '50s, the absolute worst was the North Star - Merlin engines.

The best was the Viscount - much faster than the North Star.

DC-3/6/7, Stratocruiser, Constellation all quite reasonable except that the Connie rear toilets were loud and vibrating. But by comparison with the North Star Merlins, everything else was quiet;)

[FlightlessParrot]

My recollection of the 707 was that it was rather quiet in the front (mostly wind noise) and quite noisy aft of the engines (with some vibration at times). The back of a DC-9 could be quite noisy, with a beat between the notes of the engines.

[longer ron]

I agree FP - the 707 did seem quite quiet,I seem to remember that the DC8 was a little noisier,perhaps air conditioning noise ?? it has been quite a while since I flew in either - not since 1985 I should think.

[Mr Mac]

Pax Britanica
Have to agree with you re 707 as I spent a lot of time on them, and the DC8 as a child on long haul to and from Chile. In fact the Beatles song Back in the USSR sounds as though it has one on the opening few seconds on finals. The VC10 I only flew on 3 times and agree it was noisy externally, but I thought Trident was worse for some reason. Prop experience on classics is limited to DC3,4,6,VIKING,ARGONAUT,VISCOUNT,BRITANIA, and of course the more modern 748, ATP, and various Bombardier products. As I was quite young ie under 5 for DC,s,VIKING,ARGONAUT, I do not have much memory though do remember a pipe separating of the outer engine on a DC6 over France and some substance spraying out. Pointed out to dear old mum, who got a Stew, who in turn got the F/E who looked at it and said yes "he thought something had happened", engine feathered on we went to LHR no Daily Mail headlines involved as from memory this was not unusual.


Kind Regards
Mr Mac

[pax britanica]

I was going to Antwerp on business witha colleague whowas frightened of flying. A dart herald was the scheduled plane to Antwerp but was leaking fluid all over the ramp as we watched from inside the terminal. that got cancelled and we end up ona Sabena 707 320 (note no B or C suffix)

We also sat well behind the wing and he was literally terrified as we spooled up for take off with a thunderous roaring because that was one noisy noisy beast . Mind you i have also been on a BOAC 707 436 and an Alitalia DC8-40 both of which were extremely noisy with a crackling vibration in spite of the monster movable noise suppressors (!!?) the latter was fitted with that moved back and forth on rails and must have been a big weight penalty for little apparent reduction in dB

[Brit312]

As an apprentice with BOAC in the early 1960s we had an Argonaut to play with, well it was supposedly to give us some piston engine practical experience. George Tippens [an old BOAC overseas engineer} was in charge of it and he told the following story.
Initially he Argonaut had exhaust stacks on both sides of the engine and perhaps because of the noisy cabin they swapped the inner stack over the engine [inside the cowling] to the outside , so with all exhaust exits pointing away from the cabin it made it somewhat quieter.
Now when the present Queen return from Kenya [ on a modified aircraft] in 1952 due to her fathers death, someone is said to have asked her did she think the cabin was quieter to which she said yes and on the word of a grieving daughter the mod went fleet wise.
Well you might ask how i remember this and it was because one of George's favourite task for us was to change the inner plugs on the Merlin with the mod fitted . Yes got the plugs out and back but my hands were cut, grazed and bleeding after trying to work around the crossover exhaust and all for a quieter cabin !!!!!

[ZFT]

As an apprentice with BOAC in the early 1960s we had an Argonaut to play with, well it was supposedly to give us some piston engine practical experience. George Tippens [an old BOAC overseas engineer} was in charge of it and he told the following story.
Initially he Argonaut had exhaust stacks on both sides of the engine and perhaps because of the noisy cabin they swapped the inner stack over the engine [inside the cowling] to the outside , so with all exhaust exits pointing away from the cabin it made it somewhat quieter.
Now when the present Queen return from Kenya [ on a modified aircraft] in 1952 due to her fathers death, someone is said to have asked her did she think the cabin was quieter to which she said yes and on the word of a grieving daughter the mod went fleet wise.
Well you might ask how i remember this and it was because one of George's favourite task for us was to change the inner plugs on the Merlin with the mod fitted . Yes got the plugs out and back but my hands were cut, grazed and bleeding after trying to work around the crossover exhaust and all for a quieter cabin !!!!!

Played with the same Argonaut. Also the ex Mexican Comet 4 possibly 4C?

Great memories

[Centaurus]

In the '50s, the absolute worst was the North Star - Merlin engines.


I can understand that. I had over 3000 hours on the Lincoln Mk 31 (Long Nose)
As a QFI in the right hand "dicky" seat wearing the old leather helmets, the noise from the starboard inner engine (RR Merlin 102 which had straight out exhaust pipes as against the RR Merlin 85 with shrouded exhausts) was extremely painful at take off power +18 boost and 3000 RPM on some occasions and +12 boost on others. I tried to reduce the pain by pressing my right hand hard over my right ear area during the take off run while backing up the four throttles with my left hand.
It was quite a relief to pull back the throttles to +9 boost for the climb.

During maritime patrols, the sonarbuoy operators in the (long) nose of the Lincoln would open the large observation window on each side of the fuselage. A deflection blade kept the wind out but the open window let in the combined noise of four RR Merlins and this could be for several hours during anti-submarine or SAR searches. After some ten hour flights the crew would climb down from the Lincoln with ringing in their ears that could last for hours. The long term damage to our hearing manifested itself to some crew members in later years although for some reason I was fortunate and at 86 my hearing is still good.

[Rosevidney1]

I've wondered if it isn't only the noise levels but the frequency of the sound produced that ought to be considered. At 78 my hearing is not good.

[ian16th]

Wasn't the noise level of the Merlins a large part of the Lancastrian's short service life?

[Liffy 1M]

Played with the same Argonaut. Also the ex Mexican Comet 4 possibly 4C?

Great memories

The instructional Comet 4C was G-APDT which did, as you say, spend some years with Mexicana before returning to the UK in about 1969. It survived as a fire service training aid at LHR until about 1990. The Argonaut, as a much rarer machine, had unfortunately succumbed some years earlier in 1982, very much the worse for wear after a similar role with the fire service.

[ancientaviator62]

When I served on 30 Sqn I was the designated 'minder' for a university team who had been tasked to investigate noise levels in the cargo compartment of the C130K. They concluded that db levels, frequency range and length of exposure were all contributory factors as was the excessive vibration levels. Their summary was 'it is the equivalent of being in a disco with a pneumatic drill operated nearby and it would not be tolerated in civilian use as a workplace/transport environment even with the use of ear defenders'. Our headsets were described as useless in this context.
You will not be surprise to hear that nothing was done at least not while I was on the 'K'.

[Centaurus]

Acquaintance of mine flew C130's in the Arctic Region. The APU was in the wheel well and the exhaust noise was horrific and exacerbated by the ice cold thick air. In those days ear protectors were yet to be used and in later years many crew members suffered premature deafness as they aged

[EDMJ]

The initiator of the thread posted a very specific question: What was the noise level in older airliner measured in dB.

So why does everyone feel compelled to post their old, boring war stories about "noisy" and "quiet" airliners, which nobody reads anyway and which do not reply to this question?

[brakedwell]

Did they have DB meters in thos days?

[DaveReidUK]

The initiator of the thread posted a very specific question: What was the noise level in older airliner measured in dB.

So why does everyone feel compelled to post their old, boring war stories about "noisy" and "quiet" airliners, which nobody reads anyway and which do not reply to this question?

Shock News: PPRuNe thread drifts (slightly) off-topic ...

[Tu.114]

Also, the interior noise level is not the same all over the aircraft.

For example, in the F70/100, the forward passenger cabin is rather quiet and agreeable to travel in, while those that dwell in the rear rows are screamed at by two compressors that (at lower power settings) may produce an audible beat while having their noses assailed by the occasional whiff from the outhouses. On the Dash, things are a bit different: from a noise standpoint, the most desirable spot is in the far back where the propellers are hardly audible. The business class however, placed in the front by people not having heeded the lessons from the big piston liners, is a different story.

[ZFT]

The initiator of the thread posted a very specific question: What was the noise level in older airliner measured in dB.

So why does everyone feel compelled to post their old, boring war stories about "noisy" and "quiet" airliners, which nobody reads anyway and which do not reply to this question?

You obviously read them!

[Heathrow Harry]

The initiator of the thread posted a very specific question: What was the noise level in older airliner measured in dB.

So why does everyone feel compelled to post their old, boring war stories about "noisy" and "quiet" airliners, which nobody reads anyway and which do not reply to this question?


That's what this place is for - if you want INFORMATION you should use Google......

Of course sometimes... someone asked about his partners first flight on a US Air 767 about 25 years ago - withing 6 hours he was able to read the date, time, flight number c/n number and a photo of the plane on here........

[dixi188]

I remember seeing Viscount and Electra First Class at the back, well away from the props.

Also remember flying from Paris to/from Nantes with Air Inter. Caravelle III very noisy one way and Caravelle XII very quiet the other way. I was sat near the front both ways and I think it was mostly aircon noise.

This was 1976 and the announcements were in French only so I asked for the safety brief in English and received a personal brief by a very pretty hostess.

[Chris Scott]

The initiator of the thread posted a very specific question: What was the noise level in older airliner measured in dB.

So why does everyone feel compelled to post their old, boring war stories about "noisy" and "quiet" airliners, which nobody reads anyway and which do not reply to this question?

He's right, of course. Just think of all the data we could have collected when passenger flying in a/c like Vikings, Connies, DC-6s, Viscounts, Ambassadors, Britannias, Caravelles, DC-7s, Comets, Argonauts (sorry, North Stars), DC-8s, (one could go on) if only we'd remembered to carry our decibel meters with us... :ugh:

It was thought that the high-pitched scream of the Dart had a particularly deleterious effect on cockpit-crews' hearing. AME Dr Ron Wambeek (formerly the "prone" pilot: :eek: more thread-drift) once told me he could tell by audiogram which seat a pilot occupied, because most of us had the inboard earpiece of our headsets off so as to communicate with each other (and visiting cabin crew) without using the intercom.

[avionic type]

The Aeroplane or the Flight magazine quoted that the toilets at the rear of the Comet 4B were not the places for a quick read or quiet contemplation ,in an article of the introduction of the model into airline service with B.E.A,never cured the problem .
Doing a Genny Balance either inside or outside the aircraft was a ear splitting experience,kept the surrounding country side awake on the night shift they were not amused.

[vapilot2004]

Did they have DB meters in thos days?

During the war, yes. In earlier times, according to an article by one H.H. Scott (the man known for early valve hifi design), attempts were made before standards were agreed upon - some devices used carbon mikes, others the best quality condenser microphones available. Some equipment setups came in the form of 4-5 wooden boxes that, in total, weighed in at over 100lbs, with batteries.

Much of the early research involved the quantification of human speech, thus the VU meter was born. This began to gather steam in the mid 1930s in the US, with industry standards coming in 1942, and international adoption in 1953. The dB meter scale was first used in the 1930s.

Noise regulation did not begin in the states until the early 1970s and specific commercial aircraft studies did not begin (understandably) until the screamin-mimi turbojet days of the 1960s - although such research was generally focused on external noise in and around airports and laws were not passed in the US until 1968.

General Radio Co. hand-held model from the early 1950s, a 4 valve unit with interchangeable microphones promised a +/-1dB accuracy on "average machine noises":

http://i68.tinypic.com/r2vpdy.png

Fully transistorized "gun type" unit from LEA of France circa 1960:

http://i66.tinypic.com/2881au1.png

A more commonly seen device from the very well known B&K of Denmark, also produced in the 1960s, took the shape used for decades afterwards and used a condenser microphone:

http://i63.tinypic.com/20scen6.png

[old,not bold]

I'm sure the noise in a DC3 cabin in the cruise was quite loud, but it was a soothing, soporific, low frequency rumble that made every flight as a passenger a pleasure.

Which leads to the observation that it's the nature of the noise, as much as its decibel value, that determines its impact on passengers.

[paulc]

Jkerman,

if you want to try a Ford Tri-motor yourself then the EAA have 1 that you can fly on in the USA - well worth it

[Heathrow Harry]

" it was a soothing, soporific, low frequency rumble that made every flight as a passenger a pleasure"

Your's must have been different from the one I used to fly in............... I think distance is rather clouding the view (or the noise)

[brakedwell]

Inside and out the BAC One-eleven took a lot of beating where noise was concerned. Painfully loud engine noise in the rear of the cabin with clunks, bangs and thuds when the landing gear was extending of retracting together with the graunching noises from (hydraulic?) flap motors etc.

[Basil]

The Blackburn Beverley's of RAF Transport Command were not very quiet at all.
Dreadful. It was a return trip to Malta in one which put me off applying for Shacks. Went for turbo-prop instead.

ISTR that the VC10 was very quiet.

[brakedwell]

It was thought that the high-pitched scream of the Dart had a particularly deleterious effect on cockpit-crews' hearing. AME Dr Ron Wambeek (formerly the "prone" pilot: :eek: more thread-drift) once told me he could tell by audiogram which seat a pilot occupied, because most of us had the inboard earpiece of our headsets off so as to communicate with each other (and visiting cabin crew) without using the intercom.

Fortunately I only spent three years on the Argosy, so my hearing is still excellent. The high pitched whistle from Dart compressors was almost painful when entering or exiting the aircraft through the front crew hatch when all four engines were running. The flight deck was also vulnerable to compressor noise.

[old,not bold]

....Your's must have been different from the one I used to fly in............... I think distance is rather clouding the view (or the noise)

Yes, maybe. Mind you, I saw the one I was talking about on the telly only the other day; G-AMRA, which I last saw 40+ years ago on its last charter to a strip just west of the Liwa Oasis, now evidently still in rude health and teaching Ewan (or was it Colin) MacGregor to fly a heavy piston/propeller aircraft, as a prelude to flying the BBME Lancaster.

I thought the old lady was still rumbling nicely.

[Chris Scott]

Yes, maybe. Mind you, I saw the one I was talking about on the telly only the other day; G-AMRA, which I last saw 40+ years ago on its last charter to a strip just west of the Liwa Oasis, now evidently still in rude health and teaching Ewan (or was it Colin) MacGregor to fly a heavy piston/propeller aircraft, as a prelude to flying the BBME Lancaster.

I thought the old lady was still rumbling nicely.

It was ex-Tornado Colin - at White Waltham. The training captain certainly wasn't old... ;) Great footage, and a particular treat for those of us who have flown Romeo-Alpha.

You said DC-3 cabin-noise was "a soothing, soporific, low frequency rumble that made every flight as a passenger a pleasure." That may well have been the case but Heathrow Harry may - like me - be thinking of the cockpit and even cabin of a C-47 (Dakota) freighter, which is what G-AMRA is. Unlike passenger versions, there's absolutely no sound insulation. It's fairly noisy, but the sound intensity and frequency of the P&W R-1890 (Twin Wasp) radials is more tolerable than I imagine the Darts with which a few Daks are retro-fitted.

[sandiego89]

....engine feathered on we went to LHR no Daily Mail headlines involved as from memory this was not unusual.....





If PPRUNE had existed back then, we would have had about 10 paqes of OMG, they had a part fall off and continued on over then channel??? followed up with pages of rebuttal, no... the crew made a professional call....no, they did not....why no divert? a few posting about Douglass/vs. Lockheed/ vs Hawker, comments on training and maintenance and a few stray comments on this being Prime Minister Wilsons fault....:E

[old,not bold]

Heathrow Harry may - like me - be thinking of the cockpit Well, I did say "as a passenger".

But I confess that what prompted that was my recollection of having to enquire on one flight from Bahrain to Abu Dhabi, perched on a load of cigarettes as supernumary to hitch a lift, why both pilots carefully put on their issue raincoats before boarding. "Because the forecast says we'll be flying through rain", came the reply.

[fleigle]

"Jkerman,

if you want to try a Ford Tri-motor yourself then the EAA have 1 that you can fly on in the USA - well worth it "

I flew in said EAA Trimotor last summer and it was noisy, however, the flight was only 25 mins so no bother.
Having experienced Viscounts and Vanguards many years ago, the Vanguard was horrible.
An earlier flight in a Britannia seemed quite quiet.
f

[Planemike]

An earlier flight in a Britannia seemed quite quiet.I well remember flying on a BOAC Britannia 102 in 1957 (NBI - LHR). It was, of course, promoted as the "Whispering Giant". Part of BOAC's publicity was that it was possible to stand a coin on its edge on the tray table and it would remain upright. I can testify that was a true statement.

A year later a flew on a BOAC Argonaut. It was certainly noisy and no, the coin would not stand up!!! Later I flew on an Air France Starliner, 12 hrs Orly to Fort Lamy, then on to Nairobi. I seem to remember it as noisier than the Argonaut. The "ringing in your ears" sensation lasted for about three days. Endured the worst air sickness, ever, on that flight.

[Chris Scott]

"Jkerman,

[...]
Having experienced Viscounts and Vanguards many years ago, the Vanguard was horrible.
An earlier flight in a Britannia seemed quite quiet.
f

Yes, the Britannia with its Bristol Protei was indeed quiet and vibration-free - particularly, someone reported, when all four flamed-out in a cu-nim :eek:.

Considering what a great engine the RR Tyne was (is?) for its day, it's a pity that Vickers couldn't produce a more tranquil cabin for the Vanguard. As Dave Reid writes above, the vibration was the problem.

I used to travel occasionally on a midnight flight EDI/LHR (£3/10/=, if memory serves) with few other pax, so that the only audible chatter was the usual stuff from the cabin crew in the galley. In my rear passenger seat, this was relieved at intervals of - perhaps - about half a minute as the next wave of resonance, apparently caused by a slight de-synchronisation of the engines, progressed aft along the fuselage skin. That may have been one of the reasons BUA's One-Elevens became so popular (despite the supposed handicap of Gatwick) when they were introduced on the GLA and EDI in 1966.

[brakedwell]

I flew RAF and Civil Britannias for ten years. There was no mechanical vibration from the Proteus engines, but the props produced a rumbling noise in the cabin in line with the engines. We had two crew bunks at the rear of the cabin in our 312F Brits and I used to find wind noise and a constant circular motion of the tail end made it difficult to sleep.

[Bergerie1]

I can remember, after many navigation sectors across the Atlantic in BOAC Britannia 312s, climbing into the crew rest bunk which was in the plane of the propellors and having an excellent sleep.

It was rather like one of those vibro massage beds - the same frequency and oh so soporific!

[b1lanc]

As a youngster, flew a number of times on DC-6s, typically trailing edge of wing seats - great visual of the oil streaming back over the wing from the cowl flaps:E I was too in awe of flying to notice the noise or vibration - just remember a pleasant hum.

Years later flew cross country on a DC-8 and was supposed to return on same but that was the year of the 'great airplane strike'. Came back on a brand new 707 and recall it being much quieter (and roomier) than the outbound DC-8 sitting in the same location. For those interested, round trip EWR-LAX first class - $350.

[Discorde]

Considering what a great engine the RR Tyne was (is?) for its day, it's a pity that Vickers couldn't produce a more tranquil cabin for the Vanguard. As Dave Reid writes above, the vibration was the problem.

I used to travel occasionally on a midnight flight EDI/LHR (£3/10/=, if memory serves) with few other pax, so that the only audible chatter was the usual stuff from the cabin crew in the galley. In my rear passenger seat, this was relieved at intervals of - perhaps - about half a minute as the next wave of resonance, apparently caused by a slight de-synchronisation of the engines, progressed aft along the fuselage skin.

The Guardsvan was fitted was a device called a synchrophaser, which was supposed to finesse prop pitch to minimise vibration. Eng 3 was the master and the synchrophaser adjusted the pitch on the other donks to match RPMs as described here (https://www.flightglobal.com/FlightPDFArchive/1958/1958-1-%20-%200188.PDF).

On the instrument panel the synchrophaser was located top right of the centre panel. The presentation was three mini (2-bladed) propellers which rotated when the slaved RPMs were out of synch. IIRC there was a switch to activate and deactivate the synchrophaser but I can't remember its location.

The 'Flight' article describes the various devices incorporated to prevent prop pitch from fining off if control of RPM was lost. A prop overspeed was considered a serious prob on the Guardsvan as it could lead to prop/engine disintegration. IIRC the drill was to reduce airspeed immediately to 125 kts.

The novel 'The Damocles Plot' by Julien Evans describes piloting a Merchantman (Vanguard freighter conversion).

[finncapt]

Iirc the VC10 had something similar but we had flight engineers who were very good at synchronising the "props"!!

Aah Vickers!!

[Chris Scott]

Hi Discorde,

Very interesting and sophisticated. It sounds as if the syncrophaser should have stopped any de-synchronous beat of the kind I assume was causing the resonance in the fuselage skin. Presumably it was selected off or u/s. How reliable was it?

As Alan notes above, the synchro meter sounds identical to the one on the VC10. But it was also on the DH 114 (Heron)... And I seem to recall that the props on the VC10 were a lot smaller, faster, and further aft. ;)

[Discorde]

We're going back more than 40 years Chris. I can't remember whether the synchrophaser was active at all times or only for the cruise. I suspect the latter. Was it reliable? As I recall the mini-props would usually be stationary, indicating RPMs in synch. If the throttle setting was changed the mini-props would spin until the RPMs were resynched. We rarely changed the throttle settings, though: fully forward for take-off, then at 1500(?) feet, reduce to 12,500 LP RPM for climb and cruise, accepting whatever IAS that setting gave. Max cont was 13,500 LP RPM and 'ops necessity' 13,000.

The synchrophaser was supposed to adjust the props such that the blades intermeshed as they rotated, as represented below, which again was supposed to mitigate vibration:

x + + x

I must get out more!