View Full Version : Britten Norman BN2a Islander

Prof Denzil Dexter
15th Feb 2003, 23:11
Anyone flown a piston engined Islander? If you have, and are familiar with the foibles of the type, read this..... Apologies to the original source, but it would be churlish not to repeat it again for those who havent seen it.

Britten-Norman BN2 XL

By a well-known ‘Flight magazine’.

Undaunted by technical realities, the design team at Pilatus Britten - Norman has announced plans for the BN2-XL, promising more noise, reduced payload, a lower cruise speed, and increased pilot workload.

We spoke to Mr. Fred Gribble, former British Rail boilermaker, and now Chief Project Engineer. Fred was responsible for developing many original and creative design flaws in the service of his former employer, and will be incorporating these in the new BN2-XL technology under a licensing agreement. Fred reassured BN-2 pilots, however, that all fundamental design flaws of the original model had been retained. Further good news is that the XL version is available as a retrofit.

Among the new measures is that of locking the ailerons in the central position, following airborne and simulator tests which showed that whilst pilots of average strength were able to achieve up to 30 degrees of control wheel deflection, this produced no appreciable variation in the net flight of the aircraft. Thus the removal of costly and unnecessary linkages has been possible, and the rudder has been nominated as the primary directional control. In keeping with this new philosophy, but to retain commonality for crews’ transitioning to the XL, additional resistance to foot pressure has been built in to the rudder pedals to prevent over-controlling in gusty conditions (defined as those in which wind velocity exceeds 3 knots).

An outstanding feature of Islander technology has always been the adaptation of the O-540 engine which, when mounted in any other aircraft in the free world (except the Trislander) is known for its low vibration levels. The Islander adaptations cause it to shake and batter the airframe, gradually crystallise the main spar, desynchronise the accompanying engine, and simulate the sound of fifty skeletons fornicating in an aluminium dustbin. PBN will not disclose the technology they applied in preserving this effect in the XL but Mr. Gribble assures us it will be perpetrated in later models and sees it as a strong selling point. "After all, the Concorde makes a lot of noise" he said, "and look how fast that goes."

However design documents clandestinely recovered from the PBN shredder have solved a question that has puzzled aerodynamicists and pilots for many years, disclosing that it is actually noise which causes the BN2 to fly. The vibration set up by the engines, and amplified by the airframe, in turn causes the air molecules above the wing to oscillate at atomic frequency, reducing their density and creating lift. This can be demonstrated by sudden closure of the throttles, which causes the aircraft to fall from the sky. As a result, lift is proportional to noise, rather than speed, explaining amongst other things the aircraft's remarkable takeoff performance.

In the driver's cab (as Gribble describes it) ergonomic measures will ensure that long-term PBN pilots' deafness does not cause in-flight dozing. Orthopaedic surgeons have designed a cockpit layout and seat to maximise backache, en-route insomnia, chronic irritability, and terminal (post-flight) lethargy. Redesigned "bullworker" elastic aileron cables, now disconnected from the control surfaces, increase pilot workload and fitness. Special noise retention cabin lining is an innovation on the XL, and it is hoped in later models to develop cabin noise to a level which will enable pilots to relate ear-pain directly to engine power, eliminating the need for engine instruments altogether.

We were offered an opportunity to fly the XL at Britten-Norman's development facility, adjacent to the British Rail tearooms at Little Chortling. (The flight was originally to have been conducted at the Pilatus plant but aircraft of BN design are now prohibited from operating in Swiss airspace during avalanche season). For our mission profile, the XL was loaded with coal for a standard 100 N.M. trip with British Rail reserves, carrying one pilot and nine passengers to maximise discomfort. Passenger loading is unchanged, the normal under-wing protrusions inflicting serious lacerations on 71% of boarding passengers, and there was the usual confusion in selecting a door appropriate to the allocated seat. The facility for the clothing of embarking passengers to remove oil slicks from engine cowls during loading has been thoughtfully retained.

Start-up is standard, and taxiing, as in the BN2 is accomplished by brute force. Takeoff calculations called for a 250-decibel power setting, and the rotation force for the (neutral) C of G was calculated at 180 ft/lbs. of backpressure.

Initial warning of an engine failure during takeoff is provided by a reduction in vibration of the flight instrument panel. Complete seizure of one engine is indicated by the momentary illusion that the engines have suddenly and inexplicably become synchronised. Otherwise, identification of the failed engine is achieved by comparing the vibration levels of the windows on either side of the cabin. (Relative passenger pallor has been found to be an unreliable guide on many BN2 routes because of ethnic consideration).

Shortly after takeoff the XL's chief test pilot, Capt. Mike "Muscles" Mulligan demonstrated the extent to which modern aeronautical design has left the BN2 untouched; he simulated pilot incapacitation by slumping forward onto the control column, simultaneously applying full right rudder and bleeding from the ears. The XL, like its predecessor, demonstrated total control rigidity and continued undisturbed. Power was then reduced to 249 decibels for cruise, and we carried out some comparisons of actual flight performance with graph predictions. At 5000 ft and ISA, we achieved a vibration amplitude of 500 CPS and 240 decibels, for a fuel flow of 210 lb/hr, making the BN2-XL the most efficient converter of fuel to noise after the Titan rocket.

Exploring the Constant noise/Variable noise concepts, we found that in a VNE dive, vibration reached its design maximum at 1000 CPS, at which point the limiting factor is the emulsification of human tissue. The catatonic condition of long-term BN2 pilots is attributed to this syndrome, which commences in the cerebral cortex and spreads outwards. We asked Capt. Mulligan what he considered the outstanding features of the XL. He cupped his hand behind his ear and shouted "Whazzat?"

We returned to Britten-Norman convinced that the XL model retains the marque's most memorable features, whilst showing some significant and worthwhile regressions.
PBN are not, however, resting on their laurels. Plans are already advanced for the Trislander XL and noise tunnel testing has commenced. The basis of preliminary design and performance specifications is that lift increases as the square of the noise, and as the principle of acoustic lift is further developed, a later five-engined vertical take-off model is also a possibility."

All in all, a wonderful aeroplane.

Chimbu chuckles
16th Feb 2003, 00:28
Ha ha...an oldy but a goody.

I have something in the vicinity of 1700+ hours in the Bongo/Brm Brm etc and while they are not as bad as some believe they are noisy enough that even though I wore DCs through all those hours I still have permanent hearing damage in my left ear!


16th Feb 2003, 10:56
Heh heh! Good stuff...

Might I suggest that the BN-2 is arguably the most succesful British post-war commercial aircraft? Dunno how many they've built now (OK, OK I know that most airframes were built in Belgium and Romania) but it was more than a 1000 yonks ago!

A sad aside - Desmond Norman died in November last year. which seemed to get overlooked here. His obit in the Telegraph might be of interest - you will need to register...


Only aircraft deisgner that I have ever met - a very nice man!

16th Feb 2003, 16:16
Whatever happened to the Norman Firecracker,
I think it was a good contender for the RAF lead in trainer, however politics got in the way and they opted for the tucano.

16th Feb 2003, 16:43
I believe the turbine engined Firecrackers were sold to private owners in the USA. The original piston engined Firecracker, G-NDNI, was still owned by Desmond Norman and is stored in Hangar 1 at Coventry airport along with the flyable Norman Freelance! There are also 4 or 5 Freelance fuselages stored in Hangar 6.

16th Feb 2003, 17:43
You lot may think it's funny but as someone who used to do the ferry/delivery flights of these machines from the Isle Of Wight to Singapore and Taiwan ( ferry tanks fitted and 10 hour stages) I am able to confirm that the description in the original post is absolutely factual.

17th Feb 2003, 09:05
Speechless - the Dowty ducted fan assisted Islander was - naturally! - G-FANS. I can recall an appearance at Farnborough one year. She became G-HGPC ("Halfpenny Green Parachute Centre") with the more usual O-540s in 1983 and has since pased on at least as far as Guyana... Praise be to G-INFO!

Don't think it caught on - guess the Optica might count?

Shaky, my dad was P2 on a DLCO Islander delivery to Wilson in 1971, though I can't recall his comments - if any - regarding noise/vibration! He also P2'd a Queen Air going the other way. Anything to avoid paying airfares...

17th Feb 2003, 12:34
A lovely beast - anyone ever [email protected] their ear on the aileron balance weights?? It don't 'alf sting! I see also that there are plans to resurrect the Trislander, too....


17th Feb 2003, 17:48
Anything come of the proposed private flying boat version? Noise and water?

Chimbu chuckles
17th Feb 2003, 22:54
Never fell foul of the aileron mass balance but I have burned a few people with the pitot heat. While flying them in PNG you would often get a villager who thought the pitot was for swinging off...turning the pitot heat on usually had the desired effect eventually...it always amazed me how long it took them to equate that burning sensation with the aircraft they were hanging off:D


18th Feb 2003, 08:52
Lovely post Prof. DD.

Some of you may scoff at the BN2 but for flying around the Highlands and Islands of Scotland, Inner and Outer Hebrides etc. there was none finer! Muddy strips in between stonewalls and sheep - nothing to beat it!

For shear variable noise and constant power I thought the original 'Melody in Metal'/'Whispering Nissen Hut' SC7 Skyvan took the cake.:D

19th Feb 2003, 15:13
:) Ah, the Islander - Poetry with Wings...

Didn't choose my username carefully for nothing....
:cool: :cool: :cool: :cool: :cool:

22nd Feb 2003, 20:00
My second ever flight was in an Islander!

I was working for Rolls Royce Derby and we got a call from RR at Crewe (who built the Lycoming under licence) asking for help. BN had fitted Rajay superchargers to an Islander to boost the high level performance and couldn't work out why the beast wouldn't perform to spec.

My boss and I took a trip down to Bembridge for a chat with, amongst others, the chief aerodynamicist Andy Coombs. At the end of the meeting he got a phone call and asked us if we would like to go for a flight as they had just fitted a new aileron to a production aircraft and he had to check it out. Ten minutes later we were at about 500 feet doing tight turns over a very bemused trawler just south of the Needles (boss not at all sure about this!). Then it was back for beer and butties in the Crab and Lobster pub in Bembridge. We then got chauffered over to Ford aerodrome and had a look at the turbo aircraft.

Lovely day out!

I sorted out the problem in a couple of weeks but by the time that the message reached BN they had given up on the idea. Nobody had bothered to tell us. Ah well, it made a nice change from working out performance data for these funny new Airbus and MRCA things!

Funny thing, though - I was strolling back from the paper shop this morning and an Islander flew overhead heading towards Blackpool Airport.

22nd Feb 2003, 21:34
Just read Norman's obit and am intrigued by mention of the "Weekender" a folding wing biplane ..

Anybody any info please. Thanks

Capt Snooze
25th Feb 2003, 07:22
Hey Chimbu

‘Never fell foul of the aileron mass balance but I have burned a few people with the pitot heat. While flying them in PNG you would often get a villager who thought the pitot was for swinging off...turning the pitot heat on usually had the desired effect eventually.’

Same procedure worked a treat on the other side of the border too.

The other problem there was that there was always at least one villager who felt that under the wing (preferably near one of the ‘300’ fuel drains), was a great place to get out of the sun and have a smoke.
After a while you didn’t even look for them. You simply waited till about five minutes after shutdown, and loudly announced ‘I can smell smoke’. The rest of the crowd would invariably find someone offending.
Had to give that up after the local military elected one day, to beat the crap out of the nearest suspect with their rifle butts.

Ahhhhh……. The good old days…..