Max-Range Flying

Most pilots never need to eke maximum range out of the airplane. For others long-range flying is the norm, the reason for having an airplane in the first place. There are many considerations-some objective, some subjective-when youre planning a maximum-range flight.

Lets define maximum-range flying as any flight planned to travel near the maximum distance the airplane can fly with the fuel on board, and have legal fuel reserves. When we think of max-range flying in light airplanes were usually thinking about a flight of three to seven hours, depending on characteristics of the specific airplane. If you take off with minimal fuel but are planning to use most of what youve got,

however, even a short flight entails some maximum-range thinking.

Obviously one of the factors vital for you to make a maximum-range flight is fuel. The amount of range you can get from a given amount of fuel depends on three things:

Power Setting: The higher the power setting, the more fuel youll burn. Generally, a 45-55 percent power setting provides maximum endurance. The higher power settings most of us usually use increase speed, but the fuel flow increases disproportionately, limiting overall range.

Fuel Management Technique: You might choose to fly at “book” fuel flows or, if engine temperatures are a problem for the engine(s) you fly, you might elect to fly richer than book (more fuel flow) or leaner than book (generally lean-of-peak exhaust gas temperature, EGT). Richer means more fuel burned, and speed does not increase dramatically with increases in fuel flow on the rich side of peak EGT. If you fly lean of peak EGT, you are in part reducing engine power, boosting the range effect of the power setting. You also get closer to the best fuel specifics, or the amount of horsepower developed per unit of fuel burned.

Wind: One of the biggest determinants of range is the wind. Headwinds hinder and tailwinds help where range is concerned. Since this is largely out of your hands, well not consider wind for the remainder of this discussion except in the next major factor to consider on maximum-range flights, the weather forecast.

Once airborne, its your responsibility to constantly monitor fuel state. Use everything at your disposal-fuel gauges, fuel totalizers and flow devices, GPS range interfaces and that fancy pilots watch. Glance outside occasionally to look for signs of fuel misting or siphoning from fuel caps and vents. Low-wing pilots can see the filler caps but not the vents; high-wing pilots can see the vents but not the caps. Check what you can see, and also watch the trailing edge of the wings for any sign of fuel draining or misting from the vents or caps you cant see.

Remember the recent case of a trans-Pacific jetliner when a passenger videoed fuel streaming from the wing, finally convincing the pilots the plane was venting fuel? The crew reportedly said they had seen cockpit indications of several thousand pounds of fuel lost, but even so, needed to be convinced to divert and land. Its very hard to get out of the mindset that everything is going as planned, even when faced with significant evidence to the contrary.

Most maximum-range pilots are very good about getting a preflight weather briefing. Fewer are diligent, however, about updating that information once airborne. Heres a true story I overheard in a discussion between two pilots at a major airshow. To protect their identities lets call them “Bob” and “Jim.”

Bob asked Jim if he had purchased a new airplane yet. Jim said yes, volunteering that his troubles with the FAA after his first airplane crashed were over. “They determined its all Flight Services fault,” said Jim. Bob asked what that meant. Jim said the hearing determined that Jims preflight weather briefing had included the winds aloft forecast from early on the day of the accident, and not late afternoon when the briefing took place. The Flight Service Specialist had referenced the wrong forecast.

Jim had been led to believe he would have strong tailwinds on his max-range flight, and planned accordingly. A weak front had passed during the day, however, and Jims flight actually faced a moderate headwind. Groundspeed was reduced and Jims airplane ran out of fuel just short of his planned destination. Jim and Bob agreed that it was Flight Services fault that Jims plane ran out of gas.

Ultimately, it doesnt matter whos at fault if you find yourself gliding down in a powerless airplane. It is your responsibility to check and re-check the weather not only before you take off, but also as you continue en route. Forecasts are well-informed guesses at what the weather might do but-as we all should know-they are not infallible. The longer the time between the release of the forecast and the time it is used, the less accurate it is.

By definition, a maximum-range flight takes time, which means your preflight weather information is getting less and less accurate as your flight goes on. You need to continually update the weather-whether through uplinks to cockpit displays or the old-fashioned way, radioing Flight Watch or Flight Service. And you need to crosscheck your actual groundspeed and fuel burn to the values you used when planning your max-range flight. If you compute youll be eating into your planned fuel reserves before landing, its time to land early for more fuel.

Your aircraft needs fuel and a relatively benign environment in which to fly. Your body has needs as well. Most important is that you remain properly hydrated-that you have enough water. Even very mild dehydration can cause dizziness, nausea, dimmed vision, headaches and muscle cramps, any of which can affect your ability to make good decisions and fly the airplane.

The effects of pilot dehydration are significant enough the FAA has added knowledge of its symptoms, effects and countermeasures to the physiological effects task area of the Practical Test Standards. The Federal Air Surgeon Bulletin recommends taking sips of cool (40-degree F) water before takeoff, and regularly in flight. As physiologists put it, if you feel thirsty, youre already feeling the first signs of dehydration. So-called “sports drinks” are good also as long as their sugar content is low, and they do not contain caffeine. Caffeinated drinks and sugar intake actually promote dehydration, and create other physiological problems-coming down off a caffeine or sugar “high” in flight can cause extreme headaches and accelerate hypoxic symptoms.

Wont this create other physiological “needs” in flight? The maximum-range pilot must be prepared for the need for waste elimination. There are a number of products designed to permit urination in flight for males and females, and to prevent a mess when used. Many pilots report they can keep the need for urination in check by eating small amounts of salty foods en route-potato chips or similar. Other foods eaten before or during flight should be what your mother called “healthful snacks,” low in refined sugars, to help keep you clear-headed.

About the worst thing you can do for alertness and hydration on a maximum-range flight is to drink a cup of coffee or a caffeinated drink, and then eat a candy bar or doughnut in the FBO before taking off, then not drink water regularly en route. How many times is that exactly what we pilots do?

The recent commuter airliner crash at Buffalo, N.Y., has once again brought pilot fatigue into the forefront of accident investigation. Whether or not fatigue figures in the crashs probable cause, fatigue is likely a major factor in a large number of aircraft accidents. Its one of those things we all know, but that is almost impossible to definitively prove.

A few years ago I attended Bombardier Aircrafts Safety Stand-down, a three-day human factors event primarily attended by corporate and military pilots. During one presentation, the speaker asked several hundred professional pilots in the room if they had ever actually fallen asleep in the cockpit. Through anonymous, computerized voting, over 60 percent of the pilots had reported finding themselves waking up behind the controls. Fatigue can happen to the best of us.

Aerospace physiologist Dr. Samuel Strauss writes: “Fatigue is a threat to aviation safety because of the impairments in alertness and performance it creates. Fatigue is defined as a non-pathologic state resulting in a decreased ability to maintain function or workload due to mental or physical stress. Fatigue is a normal response to many conditions common to flight operations because of sleep loss, shift work and long duty cycles. It has significant physiological and performance consequences because it is essential that all flight crewmembers remain alert and contribute to flight safety by their actions, observations and communications. The only effective treatment for fatigue is adequate sleep.”

One of the biggest challenges to max-range pilots is to gauge their level of fatigue, and more importantly, to accurately predict their state of alertness not at the beginning, but at the end of a long flight. How can you be certain you wont be too tired to safely land at the end of your trip? Succinctly: You cant. Fatigue prediction is like weather forecasts-you can evaluate factors and use knowledge of your own sleep patterns to make an informed guess at how tired youll be when you get there. But-like weather forecasts-you must continually evaluate your fatigue state while en route, being ready to divert or land early if fatigue becomes an issue.

Predict your fatigue state by honestly answering these questions:

Are you a “morning person” or an “evening person?”

Are there times of the day when you get tired at the office, or when driving your car?

How much sleep do you need each night to feel rested when you wake up?

How long is your “duty day?” Is it wise to make the trip after a long day at work?

Strauss tells us fatigue first manifests itself by errors of omission (forgetting to do things), followed by errors of commission (doing things wrong, or doing the wrong things), followed by involuntary microsleeps (sleep lapses lasting from a few seconds to a few minutes). To monitor and evaluate your fatigue state in flight, you need to look for the first signs-errors of omission-because once fatigue gets beyond that level you may not even be able to recognize theres a problem. If you have readback errors responding to controllers, if you forget to change fuel tanks on schedule, if you find when running checklists to confirm your actions, youve missed some steps, or if you catch yourself “zoning out” or fixating on one task for long periods, its time to be considering alternatives to completing the maximum-range flight as planned.

The only way to reverse the effects of fatigue is to sleep. To retard the onset of fatigue:

Get plenty of rest before a maximum-range flight.

Eat and drink appropriately before and during flight.

Use noise-cancelling headsets and adjust power to keep perceived noise levels low.

Use supplemental oxygen in unpressurized airplanes, even at altitudes below regulatory requirements.

Use autopilots and cockpit automation appropriately, but keep checking weather, fuel state, ETA and other items to stay in the loop and your mind active.

Fuel, forecasts, food and water, and fatigue. These are the primary factors in the safe completion of your max-range flight. There is one other factor you may need to consider, though: Why are you trying to make a max-range flight?

If youre flying a long overwater route, or over terrain offering few suitable fuel facilities, thats one thing. But stretching your fuel, the weather and your own rope just to be able to say, “I made it all the way from A to Z without stopping!” and then coming up short a few miles from your destination isnt the smartest thing weve ever heard. And its happened.

Dont let a desire to make it nonstop to a far-flung destination obscure your judgment or convince you to take unnecessary risks. While youre performing in-flight monitoring of fuel, performance (aircraft and human) and weather, if something seems out of whack, thats your signal to land, fuel up, check weather and then make the decision whether to press on.