It was the fourteenth time the 500D helicopter had moved the drill. As the chopper rose into the air, the “long-line” became taut as the pilot pulled up on the collective. The base, weighing about 485 kg, had never been a problem before … before 23 kg of reinforcing steel had been added, before in the cooler weather and before Larry, the pilot weighing 81 kg, replaced Dave at 73 kg. Now it was July and a gentle breeze had been helping the move. As the roar from the helicopter increased, the drillers helped by lifting the ends of the base. The base rose slowly and moved towards the edge of the drill platform. Then the wind died and the torque needle crept into the red. The pilot quickly lowered the base into the shrub beside the drill and released the lanyard. Puzzled and angry, the drillers glared at the helicopter as it hung in the air.
The problem was unfamiliarity with the many variables involved in helicopter transport. There are some drill components that cannot be moved easily because of several factors: poor communications, the weight of the various drill components, the weather, the safe external load that the helicopter can carry and the distance involved. Knowing these variables, all of which affect helicopter performance, can reduce costs, increase productivity and improve safety. Communications
In a helicopter-supported drilling program there are three main parties involved who are constantly communicating: the exploration company, the drilling company and the helicopter company. During negotiations the client discusses the program with each contractor separately, but the drilling contractor and the helicopter contractor do not necessarily discuss the contract with each other prior to the start-up of operations. So it is quite conceiveable that, upon reaching the job site, the drill and the helicopter are not ideally matched. The drill components may exceed the helicopter’s maximum external carrying capacity (payload, slingload) or the helicopter may contain too much auxiliary equipment, thus reducing its payload.
During negotiations the driller should be prepared to supply the “wet” weights of his equipment and the helicopter company the safe maximum external load it can carry. A complaint from drillers and pilots in the field is that the people who do the marketing never do the drill moves, and very seldom does a project manager ever watch a drill move.
A drill move by an experienced pilot and a trained drill crew is like a well- rehearsed dance, completed with methodical precision undisturbed by the noise of the jet turbines and the helicopter blades. Without co-operation between the pilot and the drill crew, the client pays more and the driller’s-production is reduced. So it is important that both parties be trained and that the drillers in particular know which helicopter will move their drill safely.
Longyear Canada, in co-operation with Canadore College of North Bay, Ont., has made a video that demonstrates a drill move with its Aluminum Fly 38 drill rig by a Bell 206B helicopter. A video such as this or a how-to written description by each drilling company would be very valuable to all parties because drills differ as do the names of drill pieces.
Routine meetings should be held at the beginning of the drill program, after helicopter crew changes and periodically over the duration of the programs for the purpose of discussing move procedures and familiarizing everyone with the helicopter in order to maximize its usefulness. It takes a better-than-average pilot to move a drill; and in addition to being an “ace” pilot, he must be an excellent communicator. The Drill
There are many drills on the market and most of them are designed so that they can be broken down into loads less than 405 kg (1000 lb). The bbs-25, which Bradley Bros. uses, can accommodate engines that vary in weight from 357 kg (785 lb) to 543 kg (1197 lb). St. Lambert Drilling Co. uses a modified Boyles 300 jks in which all parts are less than 405 kg (1000 lb) and Heath and Sherwood Drilling (1986) uses a Boyles bbs-1 which is less than 324 kg (800 lb). Heath and Sherwood has unitized some of its equipment by putting it in baskets, thus making it easier to move.
The main problem with these light drills is that they cannot penetrate thick overburden and consistently drill deep. And, as it is with most machinery, the larger the machine the greater the productivity. So one sees with the drills a tendency to increase the size of the engine or transmission which can weigh up to 526 kg (1300 lb). The Weather
Wind, air pressure, altitude and temperature all affect the helicopter’s performance. And it is understandable that drill moves are not completed during freezing rain and snow storms. The horizontal direction of the wind can be translated into a vertical lift by replenishing the air around the helicopter blades. If there is no wind, a loaded helicopter requires forward motion to obtain the extra lift; and since some drill holes are surrounded by tall trees, this can be a problem. With an increase in altitude the pressure drops and the air becomes less dense. For example, a Hughes 500D loses 125 kg (310 lb) of useful external load between sea level and 1,524 m (5,000 ft). An increase in temperature will also affect performance. At 30 degrees, a Bell 206B at 305 m (1000 ft) is only as effective as it would be at 914 m (3000 ft) at 15 degrees C. This means a decrease in performance of about 125 kg (275 lb). All of the other variables are relatively constant, but weather is forever changing. The Helicopter
The actual load which a helicopter is permitted to carry is dependent on a number of factors which can vary from helicopter to helicopter of the same type. Upon arriving on site the pilot should show the client and the drilling company the helicopter’s weights and balance report so that all parties will have an idea as to what the maximum external load should be. The maximum external load is calculated as follows: Maximum external gross weight minus Empty weight minus Weight of pilot minus Weight of survival gear minus Weight of fuel = Maximum external load at sea level at 15 degrees C.
Three other factors which must be considered are the minimum fuel requirement, the effect of density- altitude and over-torquing. According to Transport Canada, a helicopter must carry at least 20 minutes of fuel on board. (The effect of altitude upon aircraft performance has been discussed previously.) Density-altitude graphs are available for all helicopters to determine the external load. Over- torquing of the machine for long periods can eventually cause engine and/or transmission failure. Theoretically, a helicopter at 15 degrees C at sea level with no wind can lift the maximum external load only with full (100%) power. Since pilots are trained not to exceed 95% power, this external load should not be lifted because no safety factor has been built into the formula. Pilots generally agree that 10kg taken off the maximum external load would give them a better chance in the event of an acccident and provide a safe maximum external load.
Here’s a brief description of some of the most familiar helicopters used in moving drill rigs:
* Hughes 500D. Its short over-all length and high tail allow it to get into smaller landing sites. A bubble-door can be used so that the pilot, when long-lining, can see the drill crew below. The long-line, which is generally 25 m long, is most effective in moving drills out of holes spotted in tall trees. The additional length enables the helicopter to take advantage of any wind above the trees and serves to increase safety and comfort for the ground crew.
* Aerospatiale, Astar-350B. It is appreciated because of its lifting capability, cabin space and its cabin comfort. Direct ground visibility is not available because of its body design and moves must be completed with the aid of convex mirrors and ground- to-air radio communications. Long- lining is very difficult.
* Bell 206B. For light drills less than 324 kg (800 lb), this machine provides safety, comfort and e
conomy.
* Bell 206L-1. The L-1 can carry six passengers and, as such, is a good machine for making crew changes on large drill campaigns. The doors for both Bells can be removed during the summer to give the pilot a better view of the ground. Distance
Since the design of most drill programs requires that the distance between drill moves is short, the distance does not play a major role. It becomes an important variable when the other variables are having a negative effect on the lift of the helicopter and when the drill camp is being mobilized and demobilized — a large distance requires more fuel, which reduces the external load. For example, the Hughes 500D requires 121 kg (266 lb) of fuel to travel a distance of 209 km (130 miles). If there is no fuel at the destination, then another 121 kg will have to be subtracted in order to make the round trip.
In summary, there are many variables involved in helicopter-supported drill moves. Drill programs should be designed to match the safe maximum external load of the helicopter and the conditions where the moves are to be made so that when the helicopter pilot goes to make the last decision, he can do it safely. In the future, the combination of environmental concerns, better working conditions and more efficient machinery will lead to drills being manufactured in modular components so that they can be moved safely and quickly by large helicopters such as the Bell 204, 205 and 212 series. In the design of such drills the above variables should be considered. T. J. Neelands is president of Global Geoscience Consultants Ltd. of Timmins, Ont.
Be the first to comment on "UP, UP AND AWAY"