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Posts Tagged ‘altitude’

Fun R/C quotes – Part 6

September 7, 2010 Leave a comment

Helicopter pilots are broad eyed introverts, anticipators of trouble… They know if something bad hasn’t happened, it’s about to.

There I was, out of altitude, airspeed, and ideas…

Sure you can try it, for a nominal deposit of $2500.

It can fly as fast as your wallet is deep.

I spend half my salary on R/C Helicopters. The remaining i waste.

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Categories: RC 4 Fun Tags: , , , , ,

Learning to torque roll an RC airplane

May 19, 2010 Leave a comment

Hi! We’re back to the technique lessons! This time i’ll focus on the amazing torque rolls and how you can achieve it with success.

Torque Roll

Torque Roll

You’ve seen those super low hovers and torque rolls in demonstrations and in model magazines, and you’ve probably wondered just how they are done. Super human flying ability? Hi-tech gyro gismos and big, expensive models? Certainly, you say, torque rolls can’t be in the flight plan of a sport modeler who likes to fly normal sport models can they? Well, actually, they can.

It takes practice…

It’ll take practice, of course, and plenty of it. But saying, “just practice” is like saying if you want to paint like Picasso, just start painting. The major stumbling block for most pilots is knowing just what it is you’re supposed to be practicing. And then there’s the plane. What kind of model do you need? Maybe you’re a sport modeler and don’t want an expensive “TOC” model…if that’s what it takes.

Relax. Because besides lots of practice and a good plane, learning to Torque Roll takes one more thing: a plan. And we’ve got it right here.  So read on and we’ll let you in on how the pros got to be pros at it. It’s still going to take practice, but here’s what to practice first and what to practice with.

The Right Plane

No, it doesn’t take an expensive “TOC” model. It doesn’t even take a scale aerobatic plane. It does take a plane with some specific qualities though, but you can find these qualities in some fun, economical sport models.

The plane has to have a lot of elevator and rudder authority. This is important since, while in a hover, you need to be able to maintain pitch and yaw control with the only airflow over the tail coming from the prop.

Great power to weight ratio is a big help, too. While learning, and even if you are a torque roll master, at times you will need to “get out” in a hurry. The safest direction to get out is naturally the opposite direction of our nemesis, the ground. To hang on the prop and to blast out vertically, you need great, reliable power.

The catch-22 of torque rolling is that practicing up high gives you the altitude you need to recover when you get crossed up, but it’s a lot harder to do. Learning torque rolls lower to the ground is much easier, because you can see much better and make corrections faster, but one mistake and it’s that old nemesis again…CRUNCH!! So try to practice with as much altitude as you can.

Step 1

Like learning to ski, you need to know how to fall down and get back up first. You WILL make mistakes, even when you have it mastered. So, don’t worry about how to control the torque roll yet. Concentrate on learning to catch the model and fly out of any mistake without losing altitude, regardless of the attitude the model falls into. This is the key to the torque roll.

How to do it: At a safe altitude, pull the model vertical at about 1/4 throttle and begin to hover. Use just enough throttle to pull vertical, but not enough to sustain a hover. Let the model begin to fall out- it may fall to the side, the top, bottom or any combination. Practice catching it with the correct elevator and/or rudder input, and get the throttle in it. Focus on flying out level. After you start to get the hang of it and react faster, fly out vertical.

Trickiest Part: Don’t get confused and give the wrong input. Be careful, especially when the model falls with the nose toward you. That’s why we start at a nice safe altitude.

Step 2

You’ve now crossed the biggest hurdle to learning the torque roll. You can recover, no matter which way the model falls out. You have confidence that you can save the plane every time. Now you can concentrate on two new things. First, work on reacting with the correct rudder and elevator inputs to keep the model vertical. (The good news is Step 1 has already sharpened your orientation and reaction skills.) Second, learn to “fly” the throttle stick to maintain altitude in a hover but not climb or drop.

How to do it: Now it’s time to bring it down to a lower altitude. Start at about 25 feet, low enough to see the model and still high enough to give you a little reaction time before terra firma. Again pull to vertical, only this time add a little more power so that the model hangs motionless in the air. Once you’ve got the throttle figured out, concentrate on flying the rudder and elevator to keep the model vertical. Don’t worry about ailerons, they aren’t going to do much while you’re hovering. This is simply a balancing act, like riding a unicycle. The model may hover or it may begin to torque roll to the left. Don’t worry about rolling, this happens on its own and you don’t need to make it roll. The model will begin to roll once it is very close to dead vertical. The better you can hold the model vertical, the faster it will torque roll.

Hint: Choose a calm day to practice. Wind makes torque rolls much harder. You will also need lots of control surface throw to maintain control. Use as much as you can get, similar to a “3D” set-up if possible. While you’ll need this much control at times, it also makes it much easier to over-control the model, so use some expo. I suggest about 25% on rudder and 40 to 50% on elevator. Now you’ll have the control power when you need it, but a soft feel around neutral so you won’t over-control when making little corrections.

Trickiest part: Learning to keep up with the model’s orientation as it rolls to give the correct elevator and rudder inputs. It takes time to get good. One wrong input and the model will fall out, but you know how to fly out of a mistake, so set up and try again. Also don’t over-control. Even too much of the right correction will make you fall out. Flip back to low rates as the model falls out so you don’t over control and stall the plane. Use that expo feature in your radio.

Once you’ve got the hang of it, try backing the throttle down a few clicks as you are torque rolling and slide the model down closer to the ground. And that, in a nutshell, is just about it. So now that you’ve got a plan and you know what kind of plane, all that’s left is practice, practice, practice…

You’ve seen those super low hovers and torque rolls in demonstrations and in model magazines, and you’ve probably wondered just how they are done.

Super human flying ability? Hi-tech gyro gismos and big, expensive models? Certainly, you say, Torque Rolls can’t be in the flight plan of a sport modeler who likes to fly normal sport models can they? Well, actually, they can.

It takes practice…

It’ll take practice, of course, and plenty of it. But saying, “just practice” is like saying if you want to paint like Picasso, just start painting. The major stumbling block for most pilots is knowing just what it is you’re supposed to be practicing. And then there’s the plane. What kind of model do you need? Maybe you’re a sport modeler and don’t want an expensive “TOC” model…if that’s what it takes.

Relax. Because besides lots of practice and a good plane, learning to Torque Roll takes one more thing: a plan. And we’ve got it right here.

So read on and we’ll let you in on how the pros got to be pros at it. It’s still going to take practice, but here’s what to practice first and what to practice with.

Aerobatic Maneuvers – Part 7 (Split S)

The figure starts with a half roll to inverted followed by the second half of a loop downward.

Split S
Split S

This is another maneuver to reverse direction. This one, like the “Immelman”, does not preserve speed and altitude. In this case it trades altitude for speed.

Aerobatic Maneuvers – Part 6 (Immelman)

We’re back to this series on Aerobatic Maneuvers. If you did not follow previous posts, you can check all of them at the R/C Technique category.

Now we’ll focus on the “Immelman” maneuver. The figure starts with a half loop to inverted flight. A half roll then results in horizontal upright flight.

Immelman
Immelman

This is one of the maneuvers that have been used in WW I to reverse direction. This maneuver does not preserve speed and altitude. It trades speed for altitude.

In-Depth – De Havilland DH-88 Comet

May 7, 2010 2 comments

Hi! Welcome to this new category of this blog. Here, i’ll go in-depth on several interesting models, always looking to focus on the less common ones but surely attractive either from a history, flight characteristics, peculiarity, difficulty, style, appearance or symbolism perspective. In most cases, i’m sure a bit of all of these will apply.

To start it off in a nice way, i’ll talk about one of my all-time favorite aircrafts. Don’t ask me why, but the Comet really stands out from every other plane when i compare it with others. It’s style, unique appearance, flight challenge and twin low engine just adds to the pack!

De Havilland DH-88 Comet
De Havilland DH-88 Comet

Specs

  • Crew – 2
  • Propulsion – 1 piston engine
  • Engine model – de Havilland Gipsy Six R
  • Engine power – 172 kW / 230 H.P.
  • Max speed – 206 kts / 237 mph / 382 km/h
  • Cruise speed – 191 kts / 220 mph / 322 km/h
  • Service ceiling – 19.000 ft / 5.791 m
  • Rate of climb – 1200 ft/min / 366 m/min
  • Range – 2.542 NM / 2.925 mi / 4.708 km
  • Empty weight – 2.840 lbs / 1.288 kg
  • Max takeoff weight – 5.320 lbs / 2.413 kg
  • Wingspan – 44,0 ft / 13,41 m
  • Wing area – 212 sq ft / 19,7 sq m
  • Length – 29,0 ft / 8,84 m
  • Height – 10,0 ft / 3,05 m
  • First flight – 08.09.1934
  • Total production – 5 units

History

The de Havilland DH-88 Comet was a twin-engined British aircraft that won the 1934 MacRobertson Air Race, a challenge for which it was specifically designed. It set many aviation records during the race and afterwards as a pioneer mail plane.

Despite previous British air racing successes, culminating in 1931 in the outright win of the Schneider Trophy, there was no British plane capable of putting up a challenge over the MacPherson course with its long overland stages. The de Havilland company stepped into the breach by offering to produce a limited run of 200 mph (322 km/h) racers if three were ordered by February 1934. The sale price of £5,000 each would by no means cover the development costs. In 1935, de Havilland suggested a high-speed bomber version of the DH-88 to the RAF, but the suggestion was rejected. (De Havilland later developed the de Havilland Mosquito along similar lines as the DH-88 for the high-speed bomber role.)

Three orders were indeed received, and de Havilland set to work. The airframe consisted of a wooden skeleton clad with spruce plywood, with a final fabric covering on the wings. A long streamlined nose held the main fuel tanks, with the low set central two-seat cockpit forming an unbroken line to the tail. The engines were essentially the standard Gipsy Six used on the Express and Dragon Rapide passenger planes, tuned for best performance with a higher compression ratio. The propellers were two-position variable pitch, manually set to fine before takeoff and changed automatically to coarse by a pressure sensor. The main undercarriage retracted upwards and backwards into the engine nacelles. The DH-88 could maintain altitude up to 4,000 ft (1,200 m) on one engine.

De Havillands managed to meet their challenging schedule and testing of the DH-88 began six weeks before the start date of the race. On the day of the race, the three distinctively coloured planes took their places among 17 other entrants ranging from a new Douglas DC-2 airliner to two converted Fairey Fox bombers.

The first of the aircraft to fly was registered G-ACSP, named “Black Magic” and was bought by Jim and Amy Mollison (nee Johnson) who were both independently recognised as world record holders in their own right. This combination started the race as favorite. The “Black Magic” was the first of a great new generation of British aircraft that flew with all three of the now commonplace technical features: retractable undercarriage, variable pitch propellors and flaps.

De Havilland DH-88 Comet "Black Magic"
De Havilland DH-88 Comet “Black Magic”

The three Comets were painted in distinctive colours – the Mollisons’ G-ACSP Black Magic was black and gold; Bernard Rubins’ nameless G-ACSR was green and flown by Owen Cathcart Jones and Ken Waller; while G-ACSS, flown by C.W.A. Scott and Tom Campbell Black, was resplendent in red and white and named Grosvenor House.

G-ACSP "Black Magic", the first of the Comets, flown  by Jim and Amy Mollison
G-ACSP “Black Magic”, the first of the Comets, flown by Jim and Amy Mollison
G-ACSR - the green one - landing in Baghdad on its  way to Australia
G-ACSR – the green one – landing in Baghdad on its way to Australia
G-ACSS "Grosvenor House", winner  of the MacRobertson Trophy
G-ACSS “Grosvenor House”, winner of the MacRobertson Trophy

Grosvenor House

“Grosvenor House” went to Martlesham for RAF trials in 1935 and, painted all white as K5084, was a memorable feature of the 1936 Hendon display. It was subsequently damaged when landing with a full load and disposed of as scrap. F.E.Tasker then acquired it and Essex Aero Ltd rebuilt it at Gravesend with Gypsy Six series II engines driving DH variable pitch airscrews. In pale blue and renamed The Orphan, G-ACSS was flown into fourth place in the 1937 Marseilles-Damascus-Paris race by Flg Off A.F Clouston and George Nelson.

Bearing a third name, “The Burberry”, the aircraft left Croydon on November 14th 1937 piloted by Clouston and Mrs Kirby Green, who succeeded in lowering the out-and-home record to the Cape to 15 days 17 hours. Carrying its final name, Australian Anniversary, it left Gravesend on February 6th 1938, but broke no records after the undercarriage collapsed in Cyprus. The last historic flight by ‘SS was one of its greatest. Flown by Clouston and Victor Ricketts, it took off from Gravesend on March 15th 1938, reached Sydney in 80 hours 56 minutes, crossed the Tasman Sea to Blenheim, New Zealand, in 7½ hours, stopped overnight, then returned to Croydon on March 26th. The 26,450 miles had been covered in 10 days 21 hours 22 minutes to set a record which still stands. The Comet then returned to Gravesend where it remained under tarpaulins until rediscovered in 1951. The DH Technical School then restored it to its original MacRobertson condition for display at the Festival of Britain Exhibition, after which it was preserved by the makers at Leavesden until handed over to the Shuttleworth Trust in 1965.

Flights and Records

On December 20th G-ACSR, suitably renamed Reine Astrid, left Evere, Brussels, piloted by Ken Waller and Maurice Franchomme, to carry the Christmas mail to Leopoldville in the Congo, arriving back on December 28th. It was then sold to the French government as F-ANPY and lowered the Croydon-Le Bourget record to 52 minutes during delivery by Hubert Broad on July 5th 1935. In the course of experimental work for a projected South Atlantic mail service, Jean Mermoz made Paris-Casablanca and Paris-Algiers high-speed proving flights in this machine in the following August and September.

A fourth Comet, registered as F-ANPZ, was built for the French government with a mail compartment in the nose. In their experiments with high-speed aircraft providing a mail service to far-flung colonies, the French also produced the Caudron C641 Typhon, an aeroplane that bore an uncanny resemblance to the Comet.

The Portuguese government had similar mail-carrying ideas, and acquired the Mollisons’ Black Magic for a projected flight from Lisbon to Rio de Janeiro. Renamed Salazar and re-registered as CS-AAJ, it was ferried from Hatfield to Lisbon on February 25th 1935 by Senor Carlos Bleck and Lt Costa Macedo, who covered the 1,010 miles nonstop in six hours five minutes. A return trip was made in the following September, and in 1937 Macedo again brought the aircraft back to Hatfield for overhaul; he made an outstanding return flight to Lisbon in five hours 17 minutes in July of that year. Shortly after being sold to Portugal, the “Black Magic” disappeared for a number of decades until it was found languishing on a portuguese farm and recovered to the UK. After passing through a number of owners, “Black Magic” now resides in a safe and secure environment with her own workshop. G-ACSP “Black Magic” is now in the process of a complete restoration to airworthy condition by the Comet Racer Project Group. Although a number of years away she will one day make her second “maiden” flight from the safety of her new home at Derby Airfield.

The last Comet

A fifth and final Comet named “Boomerang” was built to the order of Cyril Nicholson, who planned a series of attempts on the major long-distance records. Piloted by Tom Campbell Black and J.C.McArthur it made a record Hatfield-Cairo non-stop flight of 2,240 miles in 11 hours 18 minutes on August 8th 1935 during the first stage of an attempt on the Cape record. This was abandoned because of oil trouble, and the machine returned non-stop in 12 hours 15 minutes and established a new out-and-home record to Cairo. Although entered in the round-Britain King’s Cup Race of September 7th 1935, “Boomerang” was a non-starter and left a fortnight later for a second attempt on the Cape record; airscrew trouble over the Sudan on September 22nd compelled the crew to abandon the aircraft by parachute.

Radio Control Scale versions

To spice up your apetite, here’s an amazing 1/4th scale (3.35m wingspan!) radio controlled DH-88 Comet flight video. This awesome scale version can be powered up by two O.S. 160-200 size engines (2 or 4 stroke) for an amazing realism. Enjoy!

[to be continued… check back later]

Aerobatic Maneuvers – Part 2 (Loop)

Here i am again to talk about more aerobatic maneuvers. This time, let’s focus on the loop.

Loop
Loop

This is one of the most basic maneuvers, but not easy to fly well. It has to be perfectly round, entry and exit have to be at the same altitude. The difficulty in flying this manuever well is in correcting for effects of wind drift. In competition, it helps if you don’t have to fly first, so you can watch what your competitors are doing and judge the wind drift that you have to take into account.

The maneuver starts with a pull up of about 3-4 g. Once past the vertical, the back pressure on the elevator is slowly relaxed to float over to top of the loop to keep it round. Past the top, the back pressure is slowly increased again throughout the back part till horizontal flight. The plane has to stay in one plane with the wings orthogonal to the flight path. Rudder is used to maintain the plane of the figure and ailerons are used to maintain the orientation of the wings.

Aerobatic Maneuvers – Part 1 (Rolls)

April 30, 2010 Leave a comment

Tired of flying straight & level ?  I’ll describe in detail all of the wildest aerobatic maneuvers for you to try!

This will be a list of aerobatic figures that have common names. Some of these were invented during aerial combat in World War I. I have also included a short verbal description and the IAC symbol for each basic figure.

The symbols for the figures follow the rules of the FAI for depicting aerobatic figures. The figure starts at the small solid circle and ends at the vertical bar. All aerobatics figures start and end from horizontal lines in either upright or inverted flight. In aerobatics competition, most figures can be entered and/or exited from either upright or inverted flight. This affects the difficulty numbers for the figures. In general, the altitude at which the figure is entered does not have to be the same as the exit altitude. Exceptions are for instance the Cuban Eight, all full loops (regular loop, square loop, etc). In cases where the entry and exit lines have to be the same altitude, they are drawn slightly separated to better show them.

The elements used in these figures are horizontal, vertical and 45 degree lines. These describe straight flight in these directions. Solid lines describe upright flight, dashed lines describe inverted flight. Parts of loops connect these line segments (see e.g. the Humpry-Bump). Rolls in 1/4, 1/2, 3/4, etc increments up to 2 rolls can be added to the lines.

The looping portions in almost all figures have to have the same radius in all parts of a figure. For instance the quarter loops going into and coming out of a hammerhead have to have the same radius. There are some figures where this does not apply completely.

Rolls on vertical lines and on 45 degree lines have to be centered on this line to score well. Any deviation from the center results in a downgrading during a competition.

In this first post i will start explaining rolls, but come back and check later for all the aerobatic maneuvers, as i will be explaining all of them.

Rolls

Rolls can be added to most other figures to increase the difficulty factor of the figure. There are two basic types of rolls: slow rollss and snap rolls (flick rolls in european parlance).

Slow Rolls

1)

Slow Rolls 1
Slow Rolls 1

2)

Slow Rolls 2
Slow Rolls 2

Slow rolls have to be flown normally on a straight line (exception is the avalanche). The roll rate has to be constant and the longitudinal axis of the plane has to go straight. This requires constantly changing rudder and elevator control inputs throughout the roll. Hesitation or point rolls include stops at certain roll angles. The number on the base of the roll symbol describes the number of points the roll would have if it were a 360 degree roll. Allowed are 2 point, 4 point and 8 point rolls. The fraction on the arrow of the roll symbol describes what fraction of a full roll is to be executed. If no points are specified, rolling is done without hesitations. If no fraction is specified, a roll symbol that starts at the line specifies a half roll (see description of the Immelman). A roll symbol that crosses the line specifies a full roll (first figure). The second figure shows the symbol for 2 points of a 4 point roll (adding up to half a roll) from upright to inverted flight.

Snap Rolls

3)

Snap Rolls 1
Snap Rolls 1

4)

Snap Rolls 2
Snap Rolls 2

Snap or flick rolls also have to be flown normally on a straight line. A snap roll is similar to a horizontal spin. It is an auto rotation with one wing stalled. Figure 3 shows the symbol for a regular snap roll, figure 4 for an outside snap. In the regular snap, the plane has to be stalled by applying positive g forces. In an outside snap, the plane is stalled by applying negative g. In both cases rudder is then used to start auto rotation just like in a spin.