The view through the 'Head-Up Guidance System' (HGS) of the Boeing 737-800.

                                     Image by Steve Ruttley.

     Check back here for the upcoming 'Blog Post' on Head Up Displays.

Hi All, here's something a little different today.....

The De Havilland aircraft company had a fine tradition of civilian training and touring aircraft prior to the outbreak of World War Two. From Humming Birds and Hornet Moths to Dragons and Albatross, the British company produced a vast range of machines. At the upper end of the speed spectrum was the twin-engined monoplane, the DH88 Comet. Manufactured from wood, the Comet blew away the competition in the 1934 MacRobertson Air Race from the UK to Australia, though just as significantly, it planted the seed for a revolutionary military aeroplane. The DH 98 Mosquito.

The Mosquito was originally conceived as a high speed unarmed bomber. In 1940 with Great Britain facing its darkest hour and a shortage of resources, it needed aircraft and it needed them quickly. Though the Air Ministry had some reservations about the unarmed aspect of the design, it could not argue with de Havilland’s expertise in wooden aircraft production techniques. Additionally, the fact that its construction called for minimal amounts of treasured metal resources offered up a viable alternative.

After a series of changes in the aircraft’s perceived role, the original order was modified to a requirement for 20 bombers and 30 fighters. The prototype initially built in a hangar disguised as a barn at the home of de Havilland, Hatfield. It narrowly missed being destroyed during a successful Luftwaffe bombing raid on Hatfield that did spell the end of a number of materials and over twenty people. However, the Mosquito survived and undertook its maiden test flight in November of 1940 at the hands of Geoffrey de Havilland’s son of the same name. During the subsequent trials the Mosquito’s speed established it as the fastest combat aircraft on either side of the conflict; a title it held for the next two years.

Into the Fray.

The Mosquito’s first operational sorties were in the role of Photo Reconnaissance (PR) in August 1941, a task it was ideally suited to with its high speed. Early in 1942, the aircraft began to see service as fighters and bombers. The Mosquito had far exceeded the original specifications and through minor modifications was able to carry 500 pound bombs in place of the originally planned 250 pounders. The first bombing raid was a daylight strike on Cologne after a “1000 bomber” raid had taken place the previous evening.

The versatility of the Mosquito became apparent and aside from being a fighter, bomber and photo recon aircraft, it successfully served as successful night-fighter and even participated in the “Hunter/Killer’ pairing of Turbinlite operations. The Mosquito was also extensively used in the precision-navigation role of ‘Pathfinder’ where it would fly in advance of the main bomber force to mark the target with incendiary ordinance. BOAC (the forerunner to British Airways) even used civilian registered Mosquitoes during the war to run the gauntlet between Britain and neutral Sweden on a regular air service. There seemed very little that the Mosquito could not do.

Special Roles

In its time, the Mosquito was called upon to fill some rather niche roles that have gone down in folklore. Two of these were 618 Squadron’s use of the bouncing bomb ‘Highball’ and the breaching of prison walls in ‘Operation Jericho’.

While much has been written of Barnes Wallis’ bouncing bomb and the Dambusters raid on the Ruhr Dams, there was an alternate deployment of the bouncing bomb planned for use by the Mosquito. This version of the bomb was known as ‘Highball’ and while the Dambusters used a cylindrical style bomb, ‘Highball’ was far more spherical.  Also conducted under a great veil of secrecy, 618 Squadron was tasked with using the bomb in an anti-shipping role with its number one priority the sinking of the German battleship the Tirpitz. Unfortunately, despite all of the effort and training, 618 Squadron never had a shot at the Tirpitz and eventually the squadron was deployed elsewhere.

A task for the Mosquito that did see notable fruition was ‘Operation Jericho’. Conceived in 1943, this mission involved an attack on the Amiens Prison in France which was holding amongst others, numerous members of the French Resistance who were scheduled to be executed. The daring low level attack took place on the 18th February 1944 and included squadrons from the RAF, RAAF and RNZAF. Its plan was to destroy the prison walls to facilitate the escape of the inmates, with an alternate plan of destroying the prison outright should this fail. It did not, and while there was loss of life, hundreds of prisoners were able to escape.

The Numbers

To quote specifications for the Mosquito is akin to comparing racehorses; there are so many types and so many variables.

In essence, the Mosquito was a twin-engined combat aircraft of primarily wooden construction. It was operated by two crew, including the pilot, and whether the second crewman was a navigator, bomb aimer or radar operator was dependent upon its designated role.

Powered by two Rolls Royce Merlin engines, it could carry nearly two tonnes of bombs deep into the heart of Germany. As a fighter it could carry 4 × 20 mm Hispano cannons in the fuselage and 4 × 7.7 mm (.303) Browning machine guns in the nose. Some photo reconnaissance versions had a service ceiling of 40,000 feet and a number of marques had a top speed in excess of 400 mph.

Ultimately, nearly 8,000 Mosquitoes were built and of these around 6,700 were delivered in wartime. As an aircraft it was not purely versatile, it was truly prolific as well.

The End.

As with all types, a number of Mosquitoes met ignominious ends on scrap heaps at the end of the war. However, several models survived and the Mosquito production line remained open until 1950. They saw service with air forces around the world and saw action with the Israeli Air Force during the Suez Crisis. A less adventurous tasking involved duty as target tugs while others took to the seas as a carrier-borne variant sporting folding wings.

To the very end, the Mosquito continued to fill roles that no other aircraft could. The model continued onto the Mk. 43 which was a trainer with the RAAF, but there were so many variants and marques before the final propeller stopped.

I had the pleasure to be interviewing a ‘Battle of Britain’ veteran who in 1942 received a new posting to a Mosquito squadron with some trepidation. He had heard very little of the new type other than the fact it was wooden and therefore seemingly a backward step in fighter technology.

He went on to fly the Mosquito more than any other aircraft and commanded a Mosquito squadron post war. He never lost his affection for the ‘Mossie’ he grew to love and sixty years later still had a twinkle in his eye when remembering de Havilland’s “Wooden Wonder”.

Overhead Sydney's Kingsford Smith Airport.

Hi All,

As the numbers continue to soar on this blog and a new group of readers join us, I thought it would be worthwhile to re-visit five of the most popular aviation blogs thus far. Here they are.

1. Golden Days.

2. So You Want to be a Pilot?

3. The Fatal Stall.

4. A Glimpse of the 'Red Tails'.

5. The Big Bang Theory.......of aircraft engines.

For those of you new to this aviation blog, welcome aboard! And for those that are continuing to come back, thanks for your support and please enjoy the growing list of original content.

Cheers

Owen

In 1994 I was a very junior First Officer in the process of completing line training with the now ‘late’ Ansett Australia. To my left sat one of Ansett’s most experienced training Captain’s on the 737 who had been on the type since the earlier -200 model had been introduced. I was to be the pilot flying on the sector, a simple hop from Melbourne to Adelaide with clear skies and fair winds, ideal for a ‘bog rat’ like myself attempting to master my first RPT jet.

Cleared for take off on runway 27 I pressed the TOGA buttons to bring the aircraft to life. The autothrottles promptly advanced, hunted a moment for the correct N1 and then held steady. Through “80 knots”, “V1” and “Rotate”, the 737-300 eased into the sky with a minimum of effort. I called for gear up and seemingly no sooner than the undercarriage had nestled into their respective bays, we heard a ‘thump’. Wonderfully indistinctive, the sound was significant enough to be met with a mutual and instantaneous turn of our heads. This was followed by one of those dreaded flight deck phrases, “What was that?” We continued to be focused on the safe ‘clean up’ of the aeroplane and Mike scanned the dials for any sign of trouble. There only seemed to be one slight ‘anomaly’.

Sitting at the bottom of the engine instrument stack sat a pair of vibration gauges. The right hand guage spoke on behalf of the No. 2 engine and was flickering around a reading of ‘2’ units. Per our checklists, no action was required until a reading of ‘4’ was evident and all other engine indications were normal. We were all aware, and wary, of information provided solely on the basis of vibration gauges. They had been integral in the loss of a 737-400 at Kegworth in England five years earlier when an engine failure had been misidentified and the incorrect engine shut down. The vibration guage only indicates a level of vibration in the fan, or front, section of the engine so as I flew the aircraft, Mike set about further investigation. He delved into the touch screen on the centre console known as the ACARS (Aircraft Communication And Reporting System) to reveal further details of the engine’s operation. Within the ACARS, the various stages of the engine revealed their individual levels of vibration and again, nothing stood out. As reflected by the guage, there was only a very slightly elevated level of vibration on the fan of the No. 2 engine. We discussed the option of returning to Melbourne but there was no justifiable indication to do so.

As we topped out in the climb and rolled over into level flight, the thrust levers retarded to the cruise setting and all evidence of the vibration disappeared. The vibration guage now read zero. With all seemingly back to normal, we reviewed the event and had another look at the ACARS; still nothing of consequence. We spoke to Engineering and they had nothing further to offer. On such a short sector we continued to manage the flight and pay attention to the housekeeping duties as the marker for top of descent steadily rolled down the Nav Display. As we pitched in to descent and idle thrust was set, we scanned the engine instruments again. Nothing. Zilch. Ops normal. I decided to delay my head scratching and concentrate on the descent profile for runway 05 at Adelaide which called for a crossing of the coast at Port Stanvac and, hopefully, a smooth decelerating arc over the water to intercept final approach. At that time, Ansett procedures had a minimum ‘spool up’ height of 800’ AGL. In essence, the most efficient descent saw the Boeing glide with the thrust levers at idle until the final stage of approach when, by 800’, the thrust levers were set for power on approach. On this sector my training was bearing fruit and the descent went very close to plan.

On final, wings level, configured and coming through about 1200’ I ‘clicked out’ the autothrottle and manually eased the thrust levers up to an appropriate N1. At about this time it felt like some one had started taking to the aircraft with a sledge hammer. The No. 2 vibration flicked full circle and seemed to bounce off the stops. In a blink, Mike called “taking over” and began to retard the right hand thrust lever back with some resultant relief. The runway loomed large, too late for checklists and a go-around seemed far from prudent. We entered the flare and Mike smoothly closed the thrust levers. The shudder was gone and we touched down right on the money as the Captain pulled asymmetric reverse, not wanting to risk the starboard engine. Clear of the runway, all indications were again normal, though we taxied to the terminal without raising No.2 above idle, just in case.

We parked at the bay and completed our shutdown checklists. The ground engineer plugged in his headsets with the accompanying eardrum rupturing ‘squawk’. Before we had an opportunity to say a word he opened up with, “You gotta see this.” The comment somewhat heightened our interest. After the passengers had disembarked we followed suit and made our way to the starboard nacelle. There was blood on the lip of the cowl indicating a bird strike, but further in a number of fan blades were badly bent. Three of them through almost 90 degrees so that they were pointing forward instead of running around the inner wall of the cowling. There was further biological evidence of the demise of a feathered being that, fortunately for us, had passed through the fan blades of the high-bypass engine but totally missed the engine’s core. This had been the ‘thump’ we had heard shortly after take off out of Melbourne.

Airframe and engine vibrations on board aircraft can be very difficult to diagnose. Their severity is often a combination of such things as airspeed, airflow angle, power settings, and the like. In the event of such vibration, many checklists call for a change in altitude, attitude and airspeed as a possible remedy. In our case, the approach configuration and body angle provided the correct mix for the vibration to fully manifest. Having said that, seeing the resultant damage also reflects the durability of modern jet engines, in this case the CFM56.
Perhaps one of the most valuable lessons that day lay in the nature of the engine problems. Prior to entering the airline world I had spent much of my time training pilots in engine failures of all descriptions. Single engine practice forced landings, engine failures after take off (EFATO) and asymmetric flight in all phases and corners of the envelope. The 737 conversion continued its engine failure emphasis with V1 cuts, engine fires, turbine seizures, failures in the cruise and so on. Almost exclusively, there was a distinct loss of power with resultant yaw. This was then followed by textbook procedures, resulting in a textbook outcome. The real world does not always throw up the standard scenario. It may be a partial loss of power, totally contradictory engine indications or any combination of conflicting information. Whatever the case, the first priority is to fly the aeroplane. Don’t rush in, take a breath and attempt to gather as much information as possible and then manage the situation. Many critical errors have been made in haste.

Until the final stage of the approach on our short journey from Melbourne to Adelaide, all we effectively experienced was a ‘bump’ and an ‘in tolerance’ vibration indication that subsequently disappeared. To see the fan blades of that starboard engine you would have expected far greater drama. We are all trained for when things go terribly wrong. We have drills, procedures and checklists in place to keep the most injured aeroplane aloft. Unfortunately reality doesn’t always fall within the guidelines of a syllabus. Be it the crippled DC10 at Sioux City or the more subtle confusion of Kegworth, neither were a ‘standard’ training scenario prior to the event. Certainly, on occasions emergencies are easily read and then again, sometimes it’s the little things.