Aerobatic Manouver ? Derry Roll

[7gcbc]

What is a Derry Roll ?

Is it a normal 1-lateral-axis roll, or is it a slow flick/auto-rotate/chandelle or what ?

rgds

7gcbc :confused:

[Bomber ARIS]

One is flying along, straight and level.

One wishes to alter course to the RIGHT.

One does this by rolling one's aircraft to the LEFT :confused:

Roll the aircraft 270* then pull; then roll out onto desired new course, always turning to the LEFT.

It's easier done than said:}

[Arm out the window]

Derry Turn:

Knucks can probably put it better than I can, but:

1. Enter a max rate level turn L or R

2. Roll off the bank slightly whilst maintaning the G

3. Allow the nose to pitch up a tad

4. Release the G, then roll rapidly with aileron and assisting rudder towards the low wing

5. When approaching the max rate turn attitude in the other direction (having gone through the inverted attitude and out the other side), reapply the G and lo and behold, you're in a max rate turn the other way.

Apparently named after a bloke called John Derry?? who came up with it in the first place as a way of shaking off your attacker, probably very effective if you hadn't seen it before, I'd imagine.

[tinpis]

Har har I remember back in the olden daze trying to do a derry turn in a Victa 100.

Lots of tin-canning and.. KAR....FLOOP..! oh well shook off the enemy. :p

[gaunty]

Great stuff.

I remember as a boy when we used to get the B & W replay on the ABC of the Farnborough Airshows in the days when they were REAL, watching Derry doing what became known as the Derry Turn if I recall correctly.

It is a very effective way of reversing direction in the twinkle of an eye, using the all of G forces already available.

It's one of those things that is so obvious one wonders why noone thought of it before.

But then as tinpis found out maybe it needed the power of a turbine to achieve it.

I have never tried it, has anyone else in a piston, I imagine the Spitfire/Mustang types might be able to manage it

I like many others of the time then had the good fortune to see all of the early development types on show when the Brits were right up there. And yes there was the odd bringing undone.

I used to look forward to the TV show like the kids nowadays wait for the latest Harry Potter.

They are just not the same anymore as they were then really pushing the boundaries of the then technology and flight.

I have attended some airshows at Biggin Hill in the days when anything went. Watching the low level RAF Super VC10 disappear behind the hangars, wing tip only showing, as it pulled around for another pass and vertical pull up. Maaaaaaate.

Then a couple of Belgian F104s popped up out of the valley at my eye level and I'm only 5'9", wings tucked inside each other at M.999999999 shock waves 'n all pull round out of sight behind said hangars and then execute an opposition twinkle roll around each other smack in front of the display stand and below the top row of seats, at least that's what it looked like. Amaaaaaazing, 2 young maybe 20 year old Belgian kids, having the time of their lifes. The howl of those big GE's winding down at the beginning of the pull through then accelerating into the enormous crackle of reheat with a huge tongue of blue flame nearly as long as the aircraft is indelibly etched in my memory of 32 years ago. Better than sex. :) :\ :uhoh: must be getting old.:{

And I still get a tightening of you know where when I recall the Victor, Vulcan and Valiants, English Electric Lightnings (basically two huge engines with a wing attached and a little hole for the pilot to sit in between the accesory cases) doing their stuff. :ok:

[Nigel Osborn]

John did his famous turn at an airshow and unfortunately his wings came off. I remember seeing it on the news at the local cinemas. Very sad end to a good pilot.

[Felix Lighter]

Away from its ACM usage the DT is an excellent way of regaining the 'crowd line' when doing air-displays.

A 180 leaves you off-set but a DT keeps you closer to the crowd and very little requirement for use of the vertical (great for those low cloudbase displays)

Another fun trick:

1.Pull into the vertical for a stall turn,

2.Full rudder to the RIGHT approx 2secs earlier than you normally would (leaving you still going up but nose 45deg from the vert)

3.Then, roll 180deg under [to the low wing] whilst centralising the rudder.

4.Complete a stall turn to the LEFT

.... confused yet?

You'll start a stall turn to the right, finish it going left and fly away in the same direction you entered!

Enjoy :)

[gaunty]

Nigel Osborn

Yes sadly whilst the turbine gave em the grunt to use the wing technology still had a way to go.

A sad end indeed.

Felix Lighter

That's a good one, but kiddies, dont try this at home.:ooh: :yuk:

[willbav8r]

I believe JD was attempting a near M1 dive in a DeHavilland machine which subsequently broke apart (some say due to the aluminum skin "tearing" on the wing - not too indifferent from Columbia.....). Unfortunately, said machine (now in bits) impacted the crowd. :(

[tinpis]

:(

Yes gaunty one had even less success attempting a Derry turn in a Tiger Moth.

The resulting snap roll and spin recovery was fun though.

I remember seeing this newsreel at the pictures.

The DH110 first flew from Hatfield in September 1951 piloted by John Cunningham and exceeded the speed of sound for the first time the following year. Tragedy struck at the 1952 SBAC flying display when John Derry was exhibiting the DH110. Arriving with a sonic boom John Derry made a fast low pass over the airfield before decelerating into a tight circuit towards the crowd line. The aircraft was seen to suddenly pitch up then break apart. One of the engines fell into the crowd killing 28 people as well as Derry and his observer Tony Richardson who died in the machine. The crash caused great disruption of the DH110 program before the fault was attributed to a catastophic failiure of the wing leading edge. Much work had to be done on the DH110 before it was ready for production, now named Sea Vixen. The Sea Vixen was the first British fighter to be designed from the outset as a weapons system and did not carry integral guns. Instead, the Sea Vixen carried a wide range of guided missiles, rockets, and bombs for the inteceptor

Bloody 'orrible piece of arcane British blacksmithing.

[gaunty]

Hear the master himself.

John Derry on the speed of sound. (http://news.bbc.co.uk/media/audio/39176000/rm/_39176624_01_09_1952derry.ram)

It seems they still had a lot to learn about sonic booms at that time.

I must say I haven't heard a "cut glass" English accent for some time.

The interview is entirely typical of the fascination with the sound barrier at the time and demonstrates that aviation as we now know it was very definitely then "a work in progress".

We now have aircraft capable of in excess of M1.0 in vertical climbing flight.

As my dear old Grandpa used to say "a triumph of brute strength and ignorance over science."

And how the Alpha Jets display team honour him (http://users.skynet.be/marys/demo/display.htm)

[spindoctor]

Felix

Ok Tried that yesterday, you have to watch that when you apply right rudder on the way up that you need forward elevator and opposite aileron to prevent the ac from rolling on its back, otherwise it works as advertised. Another party trick is to do a stall turn to the left but at the pivot point centralise the aileron and elevator and you will do a nice little half roll and end up hanging upside down in the same direction you started (but a lot slower):D

Another way of regaining the display line is a 1 1/2 rolling turn to the inside, a derry turn and then a outside rolling turn back onto the line. Works every time.:ok:

Spindoctor

[djpil]

Another variation is right rudder, stick forward and right aileron to get a knife-edge rotation.

[7gcbc]

Gentlemen,

Thanks very much, I'm still twiddling and turning, and yawing my little f4 model on my desk as we speak - and to be honest only confusing myself over again, Felixs' and spindoc's suggestions sound like fun, might try them next week if I get the chance.

thanks for the explainations.

rgds

7g

[Chimbu chuckles]

Recently at the end of a sim session I tried my 'party trick', from mispent youth, in the 767.

Down the runway < 50'/320kias, aileron roll, back on the deck and then a climbing right turn, Derry turn at flight idle configuring in a gliding 270 turn to land back on the runway.

All went well except I didn't give myself enough room in the DT/270 to regain the centerline comfortably...4 months more then back into the sim....:} ;)

Chuckles

[Agent86]

Has anyone else read the writeup of the Aviatt Pitts S-2C in the May ed of Australian Aviation ??

None of the boring 180 deg stall turn for this beastie:
Try 540 Deg ....more like a cartwheel.... round and round again :ooh:

Sounds like fun.

[djpil]

The 540 deg rotation is not in the vertical plane but if presented to the display line properly it does look like a double rotation.
The S-2B can do it too - Greg Poe first introduced it to me.

[I'm gone!]

Gday Chuck,

Sounds like fun, did you have the motion on or off?

Last time I tried(motion on) a stall turn entry then roll off the top the sim lost the plot and we ended up leaning over heavily to the left with the "Tilt"(ala Pinball style) light on. Full reset and about 20 minutes later we finished the cyclic!

Oh the joy of muckin about in someone elses big toy:}

Cheers,
I'm gone!

[Chimbu chuckles]

Motion on....but then this sim is only about 4 years old and very flash...better than the one at Boeing:}

While S turning at low alt to get lined up, with full flaps and speed brake I got into a really bad pitch oscillation and ended up a pile of wreckage. I'm not certain, and no-one else is either, whether it was a 'sim fault' or an accurate representation of horizontal stab blanking caused by the full flap/speed brake.

Still, 4 months and I get to try again...just gotta fix the easy bit:}

Chuckles.