Friday, June 12, 2015

Jump Flying, the Rotary Version! By Dan Rose

Jump Flying, the Rotary Version! 
By Dan Rose 

This article is in no way a guide to being a jump pilot, this is written to show the rotary side of jump flying for both pilots and jumpers as the helicopter is a rare visitor to the drop zone. In this article I've tried to guide the reader through the various stages of arrangements, phases of the flight and the individual problems and pitfalls of helicopter jump flying. If you want to learn to become a jump pilot go ahead and contact your local parachute authority as they'll have the relevant material to cover for jump pilot training. I hope the below helps both pilots and jumpers understand the principles of helicopter parachute operations as I've found there's a severe lack of resources and training material for the helicopter jump pilot!

First of all, a little bit about the helicopter and why the appeal to use it as a jump platform? Most fixed wing guys would describe them as 'the dark side of aviation', 'a million bolts flying in lose formation', and I've even been told by the guy who taught me jump flying that by flying rotary I'd be going straight to hell! Joking aside if you ask any rotary pilot they'll explain to you the attraction of the helicopter, the ability to lift vertically, hover and maneuver laterally. But the appeal of the helicopter as a jump platform isn't about what the pilot likes, it's the jumper! From the jumpers point of view it's a toss-up between the appeal of jumping an unusual aircraft, and the unique exit experience a helicopter gives. With the low airspeed on the run-in, this gives the jumper the subterminal exit more commonly experienced from a base jump.

To make a start we've all heard the saying 'the weight of the paperwork has to match the weight of the aircraft before you can go', this applies just as much here! Before any jumping has even been thought of, it’s important to make sure the relevant paperwork and authorisations are in place before you carry out helicopter parachute operations. What's needed may vary from country to country depending on your Civilian Aviation and Parachute authority. I'd advise researching heavily into what applies to you the pilot, the aircraft and the parachutist before you think about carrying out any kind of drops. For a pilot in the UK he/she must hold the appropriate licence/rating to operate and to be in command of the aircraft, be a BPA approved jump pilot and cleared on the aircraft he/she is going to be operating for the parachuting role. With reference to the helicopter or any aircraft carrying out parachuting it must be approved to carry out such operations, normally in the form of a flight supplement which has been prior approved by your relevant civilian aviation authority. This supplement may state any modifications made to the aircraft, door removals, and thus any airspeed or flight conditions that must be adhered to during the jump role. Finally for the jumper most drop zones put a licence and jump limit on anyone taking part in helicopter jumping, this is quite rightly so due to the complexity and the extra skill needed to carry out a helicopter jump. After the above has been said I'd just like to again emphasise that you must research the exact requirements needed for your particular location and operation, I've deliberately kept away from exact details as this article is more about an insight into helicopter parachute operations rather than definitive rules and regulations.

One final thing to be said about paperwork is the all-important weight & balance, look closely into the weight limits and envelope of your particular helicopter and any changes that'll occur through all phases of the flight. I'm not suggesting W&B is more important in the rotary world compared to fixed wing as it's vitally important in both roles, but in the rotary role the limits are very much more restricted and envelopes very much smaller. Thus 4 jumpers exiting from a Jet Ranger will have a larger effect on C of G and control forces needed to counter it, than it would in a fixed wing aircraft. The other aspect to think about in rotary operations is lateral C of G, this is where smooth jumper exit and exit order come into play. For example on a B206 with the pilot sat right seat and 2 jumpers exiting on the right side might be within C of G limits but would cause severe control inputs while they're at the door and upon exit, unable to guarantee a smooth and stable jump run. To put simply the helicopter pilot really gets to feel the difference between a light and heavy jumper and the control inputs needed on exit! It's important to sit down prior to jumping and work out suitable exit orders to ensure the safest and most stable way for all jumpers to exit the aircraft, this will vary on type, number of jumpers and pilot judgment. Also with some helicopter types there will be C of G and airspeed limits when the doors are removed. This is due to the way the air flows around the fuselage with the doors off, the rearward C of G, the effect on the directional stability of the airframe, the compensatory effect then needed from the tail rotor and cyclic inputs needed. As a result directional control may not be possible above certain air speeds and at certain C of G positions! With all this said I'd recommend running up w&b schedules for all possible jumper/fuel configurations through the day, this way you'll know what you can and can't do as things will typically change throughout the jumping day.

With the paperwork in order and your weight and balance figured out, what now? A very important source of information for both the pilot and the jumper is a proper briefing. This is an excellent opportunity to pass your requirements ascertained from your weight & balance calculations as to jumper numbers and types of exit. This is also a chance to run down the all-important safety briefing, what the jumpers do in an emergency may vary greatly between fixed wing and rotary and they must be completely clear as to what they should and shouldn't do. The briefing should include both what to do in an emergency and normal operations, for example how jumpers enter the aircraft during rotors running boarding, sounds simple but it's all too easy to walk into a tail rotor which is conveniently placed at head height! This is also a good opportunity for a question & answer session between the pilot and jumper, you'll more than likely get the typical questions like 'can we hang off this?', 'can we hang off that?', it's essential that you make everybody clear as to what they can and can't do as you don't want questions being asked while the pilots busy on the jump run. Typically with a helicopter a jump light system may not be installed so a system to notify the jumpers as to when they're on the jump run, when to climb out and exit the helicopter needs to be agreed on. With the pilot normally sat in close proximity to the jumpers verbal warnings usually work, but everybody needs to be clear exactly what the verbal warnings will be and when they'll be given to save any confusion once airborne.

Before the jumper gets into a helicopter to do a jump, it's probably a good idea to look over the aircraft while it's on the ground and shutdown. This will give them a chance to appreciate the major differences between rotary and fixed wing. The first thing a jumper may notice is the severe lack of space! Unless you happen to be really lucky and get jump a chinook, you're more than likely to be jumping a 4-5 seat light helicopter, maybe a B206 Jet Ranger or R44. I'd recommend sitting in the helicopter prior to jumping with a rig on to get used to your sitting position and how to operate the seat belts. Once you've figured out the basics think about where the handholds are and how you'll transfer yourself from sat in the door to your exit position, this might sound easy but when the time comes to exit it'll be the difference between a smooth exit and what's technically known as a cluster f**k! Ruining the experience for yourself, your fellow jumpers and not to mention making the pilots job a whole lot harder as you faff about in the door! A very important point to note are the additional snag-up points with a helicopter, door fixings, earthing points, skid supports and skid wheel attaching points are to name but a few! This emphasises the point about looking over the helicopter before the jump, chat with the pilot as he'll be able to point out the most obvious hangup points and the parts of the helicopter you should be looking for and avoid during the exit.

Once you're familiar with the seating, seatbelt usage and snag points it's time to think about the exit. Once again sit in the helicopter beforehand and plan the exit strategy and order. Will it be a single jumper exit, multiple exits, in what order and what type of exit? This will vary hugely on the type of helicopter you're jumping for reasons I'll explain later. My best advice for this is to speak to the pilot, he'll know the limits of the helicopter type and the preferred exit type and in what order to maintain a balanced and controlled exit for yourself and the aircraft. During the exit for smaller helicopter types it's vitally important jumpers are aware not to 'push-off' from any part of the airframe, it must be a 'fall away' exit. This is due to the fact the helicopters fuselage is supported under the rotor disc just like a pendulum and any outside force pushing on the fuselage will create a swinging motion and control problems for the pilot and an uncomfortable exit for following jumpers. Smooth exits are the order of the day when it comes to helicopter jumping!

Having dedicated ground crew may also be a good idea as invariably jumper loading will be done rotors running, having someone to guide them on and get them strapped in helps greatly. Due to the smaller fuel capacity and likely weight restrictions hot refuels may be needed, a ground crew will help with this and save valuable turnaround time. Whatever your ground handlers job he/she needs to be briefed just as much as the jumpers, particularly in emergencies and any relevant hand signals used during the ground handling phase.

Okay, so the paperwork, weight & balance and briefing are all complete and everybody is clear as to what do to and when. Time to start up, as with all jump flying you're more than likely be departing close to the helicopters MTOW. Careful thought needs to be taken as to the type of departure you'll be making depending on the conditions at the time, wind, temp, a/c weight, local obstacles and noise abatement need to be taken account of. Check your flight manual and make sure you're aware of your machines torque/power limits at all phases of flight, this is especially important for the helicopter when lifting/maneuvering at low level on the airfield. This is due to the power required to keep a heavily laden helicopter hovering at slow speed, and the additional power requirements needed to make turns with the tail rotors requirement of engine power. I personally try to ensure the pickup point is into wind and clear of obstacles for a straight out departure, thus easing the workload on the engine and making my job a whole lot easier! For a rotary departure it's important to try and remain clear of certain parts of the Height/Velocity curve. Any helicopter pilot will explain to you that during single engine operations, certain Height and Airspeed combinations will give unfavourable conditions for an autorotation in the event of an engine failure. Remain clear of these combinations as much as you can giving yourself the maximum possible chance to recover in the event of an engine failure, I'd also recommend scouting the airfield surroundings for ideal set down points if you have an engine failure or other technical problems on the departure phase.

When airborne and climbing it's important to have a predetermined pattern to follow to reach the jump run and exit point, this will hopefully keep you clear of other air traffic and possibly other jump ships and drops running alongside your rotary parachute operations. After all parachutists under canopy and helicopters don't mix! This is best arranged with a prior briefing amongst yourself, your fellow jump pilots and the DZ controller so you all work efficiently together through the day. On the climb-out and the doors off it's tempting for the jumpers to dangle legs, cameras etc out of the door, this should be discourage wherever possible, this is to avoid anything departing the aircraft and hitting the tail rotor with obvious serious consequences such as tail rotor failure! It's also worth mentioning that parachutist line checks must be strictly adhered to before climbing into the helicopter for the very fact doors are open during flight and thus the increased danger of premature canopy deployment and hang ups. Although a premature deployment and hang up is a serious situation in both fixed and rotary I'd argue that it's more likely to lead to an incident when on a helicopter with the additional rotating aerofoils and the proximity to these and the jumpers. In this situation the helicopter then has the reduced ability to maintain aircraft stability compared to fixed wing and should a canopy be cut away you then pose the risk of a main/tail rotor strike and failure. In this event it's important that any remaining jumpers smother the pre-deployed canopy to reduce the chance of any part of the canopy exiting the aircraft, leaving anything hanging outside the aircraft is strongly discouraged for the above mentioned reasons. Simply said with hang ups and premature deployment prevention is better than cure, parachutists check your gear before boarding and pilots ensure everybody is properly briefed on airframe snag hazards!

As with both fixed and rotary, both types face the chances of an engine failure, this can happen at any phase of flight and the pilot must be happy he can deal with this as per his emergency drills at all times. While most fixed wing pilots might think that when the helicopter experiences an engine failure it just drops out of the sky like a brick.....fortunately for rotary pilots and their passengers this isn't so! While the procedures for engine failure on rotary aircraft differ to fixed wing the basic principles remain the same, maintaining control of the aircraft and find a suitable place to land the aircraft safely. In this fact helicopters have an easier time than fixed wing with the ability to set down in relatively small and confined areas. With an engine failure in a helicopter the procedure is called an Autorotation, a short explanation of this is where the helicopter uses the airflow from the decent to maintain rotor RPM, thus it's the airflow rotating the rotors rather than the engine. This is completed at the end with a flare and a hopeful smooth set down, with the pilot keeping careful control of the rotor RPM throughout all phases of the Autorotation. Another situation unfamiliar to fixed wing pilot is a tail rotor failure, which at some phases of flight can be worse than an engine failure! The purpose of the tail rotor on a helicopter is to counter the engine/rotor torque and give directional control, with this said I'm sure you can understand how serious is can be should it fail. Depending on the phase of flight this can be dealt with in a variety of ways, one of which is to enter an autorotation. All of the above can be complicated even further by the fact you may have jumpers inside/outside of the aircraft so make sure you're comfortable with you emergency procedures.

Once on the jump run the helicopter needs to be set up ready for the jumpers to climb out and exit, for the rotary pilot this is normally speed and power adjustments as the doors are normally already open/removed and flap configurations don't apply. As with the departure, power limits and requirements need to be carefully monitored due to the helicopter slowing and needing more power to maintain this flight configuration. It's also worth mentioning at this phase of flight pilots need to be aware of the condition known as LTE or Loss of Tail Rotor effectiveness, this occurs when the helicopters tail rotor is unable to counteract the main rotors torque effect, LTE is commonly experienced during low-airspeed high-power conditions which are both experienced during the jump run. As with most aerodynamic effects the chances of LTE will change depending on atmospheric conditions, most helicopter jumps in the UK will be done anywhere between 5000-6000ft AMSL and conditions similar to standard atmospheric conditions. Should you be operating anywhere Hot & High check your flight manual to ensure you're operating within performance limitations. With reference to the run in speed on the helicopter unless you're flying/jumping a large twin turbine you won't be hovering (much to the jumpers disgust!) and this is due to the fact high hovers require large amounts of engine power and should the engine fail at this point it would drastically reduce the chances of recovery. For this reason the run in will be done at a speed suitable for autorotation should the engine fail, with most light singles this is typically around the 50kt mark. I've been told that at 50kts and the combination of the rotor down wash the exit experience is as if you're making a still air exit from a building or as in a hover.

When the helicopter is configured, stable and you've received the 'clear-drop' from the DZ controller it's time to notify the jumpers it's time to climb out. Hopefully with the practice they've had on the ground and knowing the hand holds the jumpers will climb outside as smoothly as possible, as previously discussed the exit order and movement around the helicopter needs to be carefully rehearsed due to the pendulum effect of having the fuselage hung under the main rotor disc. As the jumpers exit (making sure they 'fall off' rather than 'push off') be prepared for shifts in CofG and the cyclic movements needed to adjust for this, after my first few lifts I soon became able to pre-empt the cyclic inputs needed as the jumpers exit the aircraft. Also be cautious with the sudden reduction in helicopter weight as they exit, unless you're quick with the collective this may lead to a sudden climb and if you're sat just below cloud level a chance of inadvertent IMC. Take your time of the first few jump runs to get used to the feel of the aircraft as they exit, it may also be a good idea to sit with an experienced helicopter jump pilot while doing a light load before you chuck yourself in at the deep end with a 20 lift cycle first time around!

 Once the jumpers have exited the helicopter it's time to descend and pick up the next load, as with all helicopter control inputs try to make this as smooth as possible. On two bladed teetering hinge rotor heads you have to be careful not to cause 'mast bumping', which may occur during the descent or when arresting an inadvertent climb after the jumpers have exited. This is where in low G conditions (typically arising from excessive forward cyclic inputs during a descent) the fuselage and rotor hub exceed angle limits causing the hub hitting the rotor mast resulting in damage and potential main rotor separation! For this reason use the collective to initiate the descent and the cyclic to control pitch and airspeed, this brings me to my next point. With some types you'll have airspeed limitations when the doors have been removed, adhere to these strictly as it's all too easy to forget this when trying to hurry the descent and pick up the next load. Ignoring these airspeed limits can lead to directional control problems as previously mentioned. As with the climb out make sure your descent and airfield joining pattern doesn’t clash with local air traffic, other jump ships on jump runs and jumpers under canopy. Keep the lookout going all the way through the descent as you're more than likely operating with a lot of activity happening in a small amount of airspace. Once you're on finals and positioning to pick up the next load be cautious of ground obstructions and personnel, this is where it's a good idea to have a designated loading area for rotors run refuels and loading jumpers under the safe control of a ground handler.

With all the above said, helicopter jumps are novel and challenging for both the parachutist and pilot. As with all types of flying, caution and a professional attitude are needed from all parties involved. I’m hoping from the information in this article it’ll allow the fixed wing pilot more information into what a rotary pilot goes through, the rotary pilot more information and a starting point on helicopter jump piloting, and the parachutist an insight as what he/she will experience on a helicopter jump. I encourage any pilot to research the above further before he/she takes up helicopter jump flying as I’m in no means an expert.....but this should give you an idea where to start and what to expect! Fly Safe!!

*Thanks to John O’Connell & Alex Law for their Technical Input!

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