Flying Boats takeoff runs

[Corsairoz]

As some of you know, I am a guide at the SolentSky Museum in Southampton and take good care showing people around our Shorts Sandringham 'Beachcomber'. I treat her as well, if not better, than any other lady I have known (but don't tell my wife I said that). I also have a collection of nostalgic stories to share with our visitors as most will prefer stories to a boring set of performance statistics.

One of the stories I tell, but have never truly verified, is that the flying boats never liked taking off on a flat calm. I tell visitors that some 'activity' is required in the water to cause the bounce that will enable the vessel to leap up onto the step, unstick, accelerate and become airborne. I tell them that sometimes launches would zig zag up and down the take off area (on lakes) to 'stir up' the water. I truly cannot remember where I got this story from.

I am not certain, but I don't think I have ever seen a flying boat take off photo in flat calm waters.

As a PPL, a physics graduate and with a passion for aviation all of that 'sort of' makes sense, but I have never seen it verified anywhere.

So, a question, is it true or am I talking rubbish to our visitors? Are there any stories of abandoning takeoffs because the surface is too calm? Did launches truly 'stir up' take off runs? Were there ever any measurable swell requirements in any flight manuals?

Thanks for any answers.

Corsairoz

http://i212.photobucket.com/albums/cc106/pondskater/229SundW.jpg

[gasax]

I only have about50 hrs on floats - so compared to may on these boards I'm a complete novice. But..


Glassy water is pretty difficult to land on and requires a specialised technique. Taking off from it is equally a challenge. During my training for the float rating in Canada we actually got stuck on an L shaped lake - it was hot so a high density altitude - which was probably a big issue on the run down to South Africa - anyhow after messing up the whole surface of a 1.5 miles long lake we just barely made it. It took about 5 runs to give us a broken enough surface to allow a single float takeoff. An interesting experience!

With a big flying boat the take off distances would be very much longer and given their fairly marginal performance I would have thought morning/evening takeoffs would have been pretty standard.

So wait for confirmation but I would expect glasy water to create all osrts of difficulties for takeoff.

[ChrisVJ]

Boats (Flying boats ) with a high wetted area are prone to a lot of drag. Wave action causes air to get under the hull and reduces it.

Jemima is a Searey and several Searey pilots have experienced what we call a "suction effect" on glassy water While on the plane (up on the step) on glassy water a very slight forward motion of the stick causes more hull area to be in contact and raises the drag enough so that between a high thrust line (above the high wing) relatively high CoG and the low drag line the nose goes down, causing more drag, etc, etc and the aircraft goes base over apex.

This is in addition to the common problem of discerning height in the last few feet of a landing on glassy water. (It can be literally impossible to judge even up to forty or fifty feet.)

One technique in float planes when taking off (as mentioned above,) is to lift a float when you have enough lift to do so reducing the drag to that from one float and allowing a heavily laden aircraft to get a little more airspeed. Flying boats don't have that opportunity.

[Double Zero]

I have heard plenty of mention of float planes / flying boats requiring wave action to get aloft; I believe Francis Chichester ( before he was knighted ) mentions it in his book 'The Lonely Sea And The Sky', when he got most of the way around the world in a Gypsy Moth he'd fitted floats to; a brilliant book, recommended.

[India Four Two]

Corsairoz,

From personal experience, I can say the takeoff run in a flat calm is very long.

In the early 1970s, I travelled on a BC Airlines Mallard from Vancouver International to Tofino airport on the west coast of Vancouver Island. From Tofino, the flight was scheduled to go on to Tahsis, a logging community in north of the Island and then return to Vancouver.

The departure was delayed for quite a while while an engineer did something "aeronautical" to the tail, which involved him lying in the tail section with his legs sticking out into the cabin! Because we were late and since most of the passengers were going to Tahsis, the captain asked my colleague and I if we would mind going to Tahsis first and then stopping at Tofino on the way back. So I got to experience a water landing and takeoff in a flying boat. :)

Tahsis is at the end of a straight 20nm long fjord, protected by mountains on either side. The landing was very smooth on the flat calm water. We landed heading north towards the town and taxied towards the ramp, the wheels came down and we taxied up out of the water.

BC Airlines Mallard at Tahsis:
http://1000aircraftphotos.com/Contributions/FordCharles/6795L.jpg

After the turnaround, we taxied back into the water, the gear was raised and we started the takeoff towards the south. The water was still flat calm. I didn't time the takeoff, but after getting onto the step, I vividly remember that it seemed to take forever. I estimate that it was well over a mile.

[Neptunus Rex]

An old mate from years gone by flew Sunderlands in the RAF. He told me of one particularly hairy take-off from a lagoon in the Pacific, after a merry night-stop. The take-off had to be abandoned after a run of several miles - far longer than it should have taken. then the Flight Engineer remembered that he had flooded the bilges the afternoon before, to keep th beer and wine cool, but had forgotten to pump them out.

Problem solved, successful second attempt and one huge drinks bill for the FE at the next stop.

[dusk2dawn]

See page 4-15 in FAA-H-8083-23 Seaplane Operations Handbook.pdf (http://www.fortlangleyair.com/docs/FAA-H-8083-23%20Seaplane%20Operations%20Handbook.pdf)

[jindabyne]

So I guess this would be a long run!

http://i205.photobucket.com/albums/bb59/malgrosse/F1-2-1.jpg

[sycamore]

Could be just touching down....

[Brian Abraham]

An extract from a document written by Capt. L.R. Ambrose on the operation of QANTAS EMPIRE AIRWAYS Catalinas across the Indian Ocean (Perth to Ceylon) during WWII (Double Sunrise flights).

As for the terminals, the take-off area at Perth could hardly have been improved upon. Clear stretches of water up to two and three miles were available with no obstacles higher than 300 to 400 ft. within fifteen to twenty miles of the site. Very occasional services were delayed due to rough water when a strong and gusty wind blew in from the southwest.

At Koggala, the take-off was not so simple due solely to the limited area of the lake. When our service first commenced operating from this lake, the difficulty did not present itself 1n spite of our having noted that there was only one dog-leg take-off path as it was the period of the southwest monsoon. and the take-off path lay only slightly out of the quite strong southwest to west wind which blew continually. With the coming of the north-east monsoon, however, ushering in as it did, long periods of calm or light cross winds, a special technique had to be devised to get the rather heavily laden boats into the air.

It was noticed at once that the heavy aircraft lay very low in the water, and that if the throttles were opened normally, the bow compartment would build up an ever-increasing mound of water ahead of the aircraft, with a consequent loss of acceleration. If the throttles were opened as quickly as possible, consistent with smooth power development, whilst the control column was held hard back, the large amount of air-screw slip acting on the quite large elevators would blow the tall down, which allowed the nose to slide over its water barrier.

Because or the drag of the large aerofoils, it then became urgently necessary to return the control column to central. Any movement of the controls from central had a marked effect on the acceleration. At the came time, however, it soon became evident that the tall needed to be raised in order to decrease the angle of attack of the mainplane and to assist the boat to the step. The most effective way, to do this was to adjust the elevator trim tabs very coarsely. In case this is not clear, perhaps it may be understood more fully if I point out that only when the aircraft reached such speed as made the controls fully effective, could the tail be raised in the normal manner. Any movements before this period would only delay its arrival by increasing the drag and only long experience and consistent watching of the air speed indicator would show its arrival. Watching for this speed would have been just something else to watch for, whereas by altering the trim tab, its drag was negligible and yet it announced automatically the arrival of the effective speed by itself acting upon the elevators and raising the tail. Immediately this movement was felt, the trim tab had to be adjusted back to the take-off setting, With practice, this could be done quickly and without reference to the adjustment scale. By now, in our take-off, the floats should be raised and the post-hump porpoise had commenced. This latter was normally stopped by a slight rearward movement of the control column, but in conditions of flat calm, it was found advantageous not to damp it right out, as the slight rocking motion tended to introduce air under, the planing bottom, and so help to unstick the boat.

From the time the craft was on the step, no further special technique was required, as it quickly accelerated to the point where it became airborne. In order to show the advantage of this drill, the following figures are given:-

vvLoadvvvvvHeadwindvvvTake-off Time
35,000 lbs.vGlassy calmvvvv90-115 seconds
vvvvvvvvvvvvv5 ktvvvvvvvv60-65
vvvvvvvvvvvv10 ktvvvvvvvv55-60
vvvvvvvvvvvv15 ktvvvvvvvv50-55

In glassy calms up to 115 seconds have been taken, but the average was 90 to 100. Using the special drill this time was cut down to from 70 to 80 seconds. Taking the worst of the latter and comparing it with the best of the former times, an advantage will be seen of 10 seconds, which, when converted to horizontal distance over the lake reckoning on a speed of 60 miles per hour (and the Catalina was going faster than this at 60 to 70 knots) shows that approximately 900 feet was saved, which in a limited take- off area, such as Koggala, represented a very valuable saving.

Once in the air, the aircraft handled quite well with its big load.

It is notable that no mention is made of any difficulty in getting the vastly overloaded Catalina off the water in glassy conditions. Due to technique mentioned perhaps?

[Mike7777777]

An overloaded Sunderland needed 5 miles to takeoff during the evacuation of Greece. Must have been over the horizon.

[Feather #3]

A bit off-topic, but have a look at this link;

Catalina returns to make a splash - ABC Mildura - Swan Hill Victoria - Australian Broadcasting Corporation (http://www.abc.net.au/local/videos/2011/03/11/3161185.htm)

Dick waxes lyrical, but the footage is interesting.

Only the 1st touch-and-go is shown. Two better ones followed [no skips] and then a landing & takeoff the next day which the ABC didn't film. Private footage may become available later.

The Kiwi's regularly do this in fresh water, but is was a first in Oz for a long time with this type.

G'day ;)

[evansb]

Great photo of the B.C. Airlines Mallard! Bit of a thread drift here, but if you're interested in amphib flying, I highly recommend the book The Pathless Way - Flying the British Columbia Coast written by Justin De Goutiere. He was a pilot for B.C. Airlines. The book is illustrated. Published in 1969 and 1972. Yup, I read it way back then.

[Krakatoa]

I remember a departure from Seletar,(Singapore) one night when the first two take off runs were aborted as we were still on the water when passing the last flarepath dinghy. This was after the launch had been up and down the take off area a few times to break up the surface of the water.
We managed to get airborne on the third attempt. I think it took us one minute fifty seconds.

[India Four Two]

Before I posted about my Mallard trip, I tried unsuccessfully to find some information about the takeoff performance.

However, I did find an Albatross pilot report, with this interesting paragraph:
The underside of the fuselage is assembled with round head rivets, while the remainder of the aircraft is flush riveted. As told to us by the owner, the Albatross was originally designed and built with flush rivets on the underside. After an operational accident, a large hole in the underside of an Albatross was repaired in the field, but the mechanic only had round headed rivets available. Much to their surprise, the water takeoff performance improved, getting off the water 5 to 10 knots sooner. Word was sent back to Grumman, who verified this with testing. Therefore, all subsequent Albatrosses were completed with round headed rivets on the hull bottoms. In an odd twist to the story, because the sheets were already dimpled/countersunk, they used a special rivet which was essentially a flat head rivet, but with a round head added on top of it. Countersunk round head rivets-only on the Grumman flying boats...
Flight Report - Grumman HU-16A Albatross (http://www.eaa1000.av.org/fltrpts/albatross/albatross.htm)

[ChrisVJ]

Brian A.

The experience with the Searey is remarkably similar though once accelerating she is off the water in about 600 to 800 feet. It is too quick really to judge any extra time taken when it is glassy.

Power up, a big wave rises in front to coaming level. Pull the column back to keep the nose up and she starts to climb up the wave, now put the stick forward to ease the drag and she slips over it onto the step Ease the stick to avoid the nose submarining but then often she'll porpoise. Ease the stick back a little further and it stops immediately and we're away.

Sometimes I look at a 747 and wonder at the fact that the essential physics that makes it fly is the same as on our GA aircraft!

[evansb]

Hard chine, mates. Way back in 1975, while flying float Twin Otters in Canada's western Arctic, a professional pilot named Dave Brown explained to me the inherent incompatability of hydrodynamics and aerodynamics. He said, "Take the McKinnon Turbo Goose, for example" Say no more.;)
http://1000aircraftphotos.com/Contributions/6150L.jpg