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PANDAMATENGA
12th Feb 2010, 00:03
Given that the Harvard(terrific as it is) was really a noisy converter can anyone tell me why it was never fitted with a 3 bladed prop!Surely this could have absorbed the considerable power in a less noisy fashion.

Thanks

Panda

Brian Abraham
12th Feb 2010, 03:00
The Australian CAC Wirraway which had as the T-6/Harvard/Texan the same ancestor in the NA-16, used a 3 blader.

tinpis
12th Feb 2010, 06:02
And Hamilton Standard would have done what with its 4 million two blade props?
Dropped them on the enemy?

StbdD
12th Feb 2010, 07:00
Maybe this Tinny

http://browningmgs.com/Images_1919A4/Photos_04-VietNam/MobileStrikeForceAirboat.jpg

(apologies for thread drift)

India Four Two
12th Feb 2010, 15:46
Without all the surplus Wasps and two-bladed props, the Beaver wouldn't have had its wonderful distinctive noise, although these days more and more have three blades.

pigboat
14th Feb 2010, 03:13
The Wirraway had the geared version of the 1340, didn't it? That's the same engine as the Otter, thus the three-blade.

avionic type
14th Feb 2010, 10:00
I,m sure P&W and Hamilton spent more time than putting a few figures on the back of a fag packet to optimise the best combination for North Americans demand for the engine / prop , I always thought that the noise was due to the fact that the engine had no reduction gear [for cheapness and relibability remember it was a training airplane] and the tips of the props were moving very fast
i'm more than ready to be "shot down in flames"

clunckdriver
14th Feb 2010, 10:39
Why would you want to make a Harvard sound any different? How else could we have kept the good citizens of Moose Jaw awake at night, or get the attention of the blonde girl driving the combine? The Harvard sounds just the way God meant an aircraft to sound, now of course we have our Air Cadet L19s modified so they dont disturb the Nimbys, I gues they would rather have kids hanging around shopping malls than making noise with airplanes! {Now I feel much better!}

Lightning Mate
14th Feb 2010, 10:56
Do I remember that at max rpm the blade tips were just supersonic, which accounted for the noise?

Fog in brain perhaps.:\

Warmtoast
14th Feb 2010, 12:40
Do I remember that at max rpm the blade tips were just supersonic, which accounted for the noise
As someone who had a lot to do with Harvards at 5 FTS (RAF Thornhill, S. Rhodesia) in the early 1950's ISTR that this turned out to be an urban myth. The diameter of the prop x the 2,600 rpm round the circumference wouldn't have led to the prop tips travelling faster than sound (760 mph). However, mathematics have improved since them and I'm willing to be corrected!

RAF Thornhill (5 FTS) 'F' Flight, line-up c. 1952 below.

http://i145.photobucket.com/albums/r231/thawes/RAF%20Thornhill/HarvardIIBs-FFlightline-up.jpg

avionic type
14th Feb 2010, 12:45
My theory also, the other plane with the same problem was the Viscont [it wasn't called the whistler for nothing] and as props lost their efficency at those speeds many a was spent trying to solve the problem but bless em they never did so lets face it the Harvard/Texan was to put it bluntly a "throw away " airplane in its prime the engine /prop combination worked and we were left with the lovely noise, long may it continue .:D:D:D

clunckdriver
14th Feb 2010, 12:52
Warmtoast, am suprised to note that they have the extended exhaust stack, we needed that for cabin heat in Canada, I also flew some in the Southern part of the World which had the short pipe and no cabin heat, mind you the drill was to block the students heat vent with bog paper, thus pushing all the warm air back to the instructors cockpit, some of those poor students from warmer climes must have frozen on a long cross country, but they all seemed to be none the worse for it on graduation day.

Lightning Mate
14th Feb 2010, 12:57
Hello Warmtoast.

"As someone who had a lot to do with Harvards at 5 FTS (RAF Thornhill, S. Rhodesia) in the early 1950's ISTR that this turned out to be an urban myth. The diameter of the prop x the 2,600 rpm round the circumference wouldn't have led to the prop tips travelling faster than sound (760 mph). However, mathematics have improved since them and I'm willing to be corrected!"

Agreed at low level, but it didnt take much of an altitude increase/decrease in temperature for it to happen.

OK mate, hat, coat, door.....

GotTheTshirt
14th Feb 2010, 13:36
At Derby Aviation in Burnaston we did the annuals on the RAF University air squadrons aircraft for several univeristies every winter.
Every autumn they would ferry in a dozen or so, Chipmunks and Harvards.

We would do the annuals and mods etc and then in Spring several Ansons would arrive with the drivers to take them back to the unis!

When they were all lined up on the tarmac they were pretty inpressive but alas I did not get any pics.

With the prop noise the Harvards sounded quite aggressive compared with the Chippie:}

Departure day meant running around with spare Koffman barrels for the Chippies as they fired all the cartridges without a start !!:ok:

Usually we got a good beat up on departure ( Days before elf an safety:))

pigboat
14th Feb 2010, 15:09
Clunk, someone on AvCanada said they used to install a two-blade on the Noorduyn JIN in the summer, to make the worlds loudest alarm clock. Just to wake up the good citizens of Red Lake. :p

Warmtoast
14th Feb 2010, 16:04
With the prop noise the Harvards sounded quite aggressive compared with the Chippie
...and just think what it was like with 21 of them!
http://i145.photobucket.com/albums/r231/thawes/RAF%20Thornhill/Thornhill-Harvards-FootballFinal.jpg



Warmtoast, am suprised to note that they have the extended exhaust stack, we needed that for cabin heat in Canada
It could get pretty parky in Rhodesia. Thornhill was 4,640ft above sea level and although being in the tropics, the Southern Hemisphere winter could be cold. Get up to 4,000 above ground level and you would be flying at nearly 10,000ft, which at night could be considered brass-monkey cold.

Photo below of the heater pipe showing how it runs into the cockpit after passing through the centre of the exhaust pipe as a rudimentary heat-exchanger. ISTR that the heat control was a butterfly-type valve in the pipe in the cockpit by the right foot that you opened as required. The pipe continued along the fuselage wall into the instructor's seat at the rear which had a similar control.


http://i145.photobucket.com/albums/r231/thawes/RAF%20Thornhill/ExhaustHeat-exchanger_1280x676.jpg

pontifex
14th Feb 2010, 16:21
I was lucky enough to fly with the Harvard Formation Team back in the late 80s. We had a "Zeke" which was a Harvard altered to look like a Zero for the film Tora Tora Tora which some may remember, and I flew it in the displays acting as No2 to Gary Newman when we got shot down by the "good guys". This delightful machine had the same engine but a HUGE 3 bladed, geared prop. The power available was awsome - you could do low level aeros all day and never lose energy. The only problem was that, for prop clearance, the UC oleos had to be pumped up rock hard and it would bounce like a ping pong ball. This meant a 3 pointer was essential. But, with the now very nose high ground attitude, it was pretty close to the stall (a sort of ground level coffin corner). As a result the private owners in its country of origin found it too much hassle which is how we got one. I would love to post a photo of it but I don,t have a web site, know anyone with one, or know of one where you can find it. Pity as it is a nice one taken from Gary's machine when we were half way round a loop. Can anybody tell me of a simple way to get it to here from my hard disk?

pigboat
14th Feb 2010, 16:26
Can anybody tell me of a simple way to get it to here from my hard disk?

Send it to me as an e-mail attachment. I'll run it through my Photobucket account and post it here.

NutherA2
14th Feb 2010, 16:50
One student on the last Harvard course at 3 FTS Feltwell in 1955 was fortunate that the aircraft had the two-bladed prop; he elected to try his hand at low flying and gave a large area of Norfolk a power cut by hitting a High Tension power cable. He flew the aircraft back to Feltwell (no doubt for an interesting interview) and I saw the aircraft after the incident. The cable marks ran along the leading edge of both wings and of the engine cowling, just below the prop shaft. It must have been near impossible to achieve this without also hitting the propeller and he would certainly have come to grief with three blades

tinpis
15th Feb 2010, 00:22
Snow S2D ag ship had the PW1340 with a two blade prop
Obviously a different prop it didnt howl.

Krakatoa
15th Feb 2010, 02:00
One of the instructors at Claresholm party piece was to take a student on the low flying exercise area and ask the student to show him some low flying. After a few minutes the instructor would say, "I have control" and push the nose down. Having frightened the poor student he would say, "that is low flying".
One day he returned to the flight line with the tips of the prop bent back about thirty degrees. If you look at the length of a Harvard prop blade I would say, "that was low flying"

India Four Two
15th Feb 2010, 13:41
However, mathematics have improved since them and I'm willing to be corrected!

Warmtoast,
I calculate that a 9' prop at 2600 rpm would have a tip speed of 835 mph, which would be about Mach 1.1 at sea level.

Of course, my mathematical ability might have been affected by the noise from my ride in "Harvard 98" at Tauranga in January. :ok:

http://i30.photobucket.com/albums/c309/india42/Harvard98.jpg

A quick cross-country to Matamata gliding club for a cup of tea, followed by aerobatics over the beach. My wife said I couldn't wipe the smile off my face all day. Of course, the earlier ride in "Stearman 03" helped too!

Warmtoast
15th Feb 2010, 16:43
India Four Two

OK I stand corrected on the tip speed reaching 835mph at 2600rpm. But that puts me in a quandary as to why all the arguments I had with others about the prop tip NOT reaching the speed of sound all those many years ago should be changed.

So a small request - show us the math you used to get to your result - please, if only to put me out of my misery!

PS. I'm very envious of your recent ride - last time I stepped out of a Harvard was in 1953.
I'm also struck by the similarity of the fuselage number to the numbering used at 5 FTS back in the early 1950's (see my photo above).

sycamore
15th Feb 2010, 18:44
Diam=9ft, circ=pi.d=28.28ft; Max rpm(normal)2250=37.5 rpsec.
28.28 x37.5=1060 ft/sec=.949M..
At 2600 rpm<20 secs(max) =43.3 rpsecs.=43.3 x28.28 =1225 ft/sec=1.1M
Add a vector for 90 KTS on t/o,tipspeed=1070 fps/ .958M.
Add a vector for 200kts @ 2600rpm,tip-speed=1255 fps/ 1.124 M

barit1
15th Feb 2010, 19:07
Actually the BT-13 Vultee Vibrator was a bit noisier. Same p/n blades, slightly different hub for the Wasp Jr. prop shaft. The Wasp Jr. turned 2300 RPM (vs the Wasp 2200) - and the BT-13 had two-position prop control (no prop governor) which meant you could wind it up past 2400 easily.

Airshow pilots in Stearmans used the Wasp Jr. BT-13 powerplant/prop package, and I shudder at the numbers I've hear them winding up to. At least two of them paid the ultimate price for their noisemaking. :uhoh:

pontifex
15th Feb 2010, 19:19
Pigboat, please PM me with your email address.

India Four Two
16th Feb 2010, 02:04
Warmtoast,

Yes, I noticed the number "dyslexia" as well. In fact, I had to do a double check, to make sure it wasn't the same aircraft.

Earlier in the day, I had flown a PT-17 and my instructor let me do three touch and goes. A lovely aircraft, just like a big Tiger Moth. I felt I would be able to solo it quite quickly. The Harvard on the other hand would take me quite a while to become comfortable in. I wasn't able to try landing it, but I did get to start it up. Clearly, you really need three hands, even after you've been shown how to wrap your leg around the stick :)

Two observations about the Harvard. Firstly, there is no elegant way to enter or exit the cockpit. It would have been rejected if Cavalry officers ran the RAF. ;) Secondly, why on earth didn't NA put in a cockpit floor? The loose article risk is huge.

Sitting there, looking out at that big roundel took me right back to my UAS Chipmunk days:
http://i30.photobucket.com/albums/c309/india42/IMG_3894.jpg

A lovely day. Three flights in three radial engined aircraft. I cannot wait to go back. They've got a T37 as well!

pigboat
16th Feb 2010, 02:13
Done, check your PM's.

Here is pontifex' photo of the Zeke. Wonderful shot. :ok:
(I resized it a bit so's it wouldn't be too big for the page.)

http://i100.photobucket.com/albums/m8/Siddley-Hawker/Zeke.jpg