RPM Warning Light Over Lake Pontchartrain
I send my four children a letter each month which includes a personal story from my days in the military. This is one of those stories.
Flying helicopters was a lot of fun while I was in the Army, but it also had its scary moments. One such time was when I was flying from Fort Polk, Louisiana to New Orleans. I was flying a UH1H (Huey) helicopter along with my copilot and a crew chief. On the north side of New Orleans is Lake Pontchartrain. The lake is 630 square miles in size and is 24 miles across from north to south. To save time when flying to New Orleans, we pilots would often take a ‘shortcut’ across Lake Pontchartrain.
Now the good think about flying the 24 miles across the lake was it saved us 15 to 20 minutes because we didn’t have to fly around the lake and circumvent civilian airfields. We could zip across the lake and land directly at the Louisiana Air National Guard base which was located right on the south shore of Lake Pontchartrain. The civilian air traffic controllers also liked our Army helicopters to fly directly across the lake to the airbase because it meant they didn’t have to worry about us getting in the way of the civilian airliners coming in to land at New Orleans International Airport.
Of course there is a bad side to everything. The bad thing for us was that if our helicopter developed some type of malfunction while we were over the lake, we’d have nowhere to land except in the water since we would be flying at a low altitude. You see, the military had a rule that we could only fly over water in our helicopters if we were high enough to glide to the shoreline if we had an engine failure, or if the crew wore water survival gear. Since it is 12 miles from the middle of Lake Pontchartrain back to the shore line that would mean with a glide ratio for our helicopter of approximately 4 to 1, we could glide about 4 feet for every 1 foot drop of altitude. With 12 miles from the center of the lake to the shore line, we would have had to be flying at a height of about 3 miles (approximately 15,000 feet). That’s doable in a helicopter, but we’d have needed to have oxygen, plus it would have taken extra time to climb that high, and of course we’d have been in the way of the civilian airliners. Suffice it to say, we opted to fly across Lake Pontchartrain at a 1000 feet while wearing water survival suits.
Anyway, there we were flying fat, dumb, and happy across the lake. And wouldn’t you know it, at about the halfway point when we were 12 miles from the nearest land, our helicopter’s low RPM warning light begins to flash and the corresponding warning alarm sounds over our intercom. Now, the low RPM warning light is designed to let the pilots know when their rotor blade is slowing down. Since the fast spinning of the helicopter’s rotor blade is what keeps the helicopter flying, having it slow down is not a good thing. Normally, having the low RPM warning light come on while you’re flying straight and level means you’re engine has stopped working. And of course, that would be a very bad thing, especially if you’re over water with the nearest land 12 miles away.
Now, you might think having an engine failure in a helicopter means it would just fall out of the sky. But that’s not the case. If the pilot lowers their collective (the control that changes the pitch in the rotor blade) fast enough, the helicopter will still begin to fall (hey, it was going to fall anyway), but with the reduced blade pitch, the air coming up through the rotor blade will keep it spinning. The spinning rotor blades sort of act like a parachute in that it slows the rate of descent, and the pilot can glide forward about 4 feet for every 1 foot of descent.
Note: To any ex-helicopter pilots who might read this story, believe me, I am well aware a variety of factors such as speed can drastically affect the glide ratio, but hey, this story is mainly written for non-helicopter pilots, so please cut me some slack. A 4 to 1 ratio explanation is just used as an average.
Anyway, pilots are trained in emergency procedures for various malfunctions such as an engine failure. Now, initiating the emergency procedure for an engine failure needs to be done quickly. If the helicopter engine stops and the collective is not lowered quickly enough (I’m talking a couple of seconds), the air resistance against the rotor blade will slow it down so much the pilot will never get it spinning fast again. Consequently, the pilot has to react quickly.
At the same time, pilots also have it drilled into them that technology can sometimes be wrong. An aircraft’s instruments are an aid, but they aren’t fail proof. In other words, the instrument telling you something is wrong might be wrong itself. That’s why pilots have it drilled into them to combine the warning from the instrument with the pilot’s other senses before making a decision. And, of course, everything has to be done quickly.
So there we were flying at a 1000 feet above the water with 12 miles to the shoreline when the low RPM warning light and alarm comes on telling us our rotor blades were slowing down. I happened to be flying at the time. When the low RPM warning light and alarm came on, one part of my mind had a split second of fear as it envisioned our helicopter crashing into the water of Lake Pontchartrain a 1000 feet below. However, another calmer part of my mind went, ‘Hmm. I did not feel the helicopter twist which should have happened for loss of torque in the case of an engine failure. And, the helicopter did not get quiet. I can still hear the noise of the engine.’ So, I didn’t begin calling “Mayday, mayday” over the radio, and I didn’t initiate an emergency procedure for an engine failure. Instead I told the copilot we had a faulty RPM warning light, and we continued flying the remaining 12 miles across the lake until we landed safely at our destination. Fortunately for us, the Louisiana Air National Guard maintenance personnel at the base were very good, and they had our faulty RPM warning light replaced in short order once we landed.
Moral of the Story: First off, you never know when something bad is going to happen. You can be going along with everything going great when suddenly out of the blue comes a dangerous situation. You can’t live in fear of something bad happening, but with proper training and backup plans (i.e. emergency procedures) you can at least have a fighting chance of getting out of the dangerous situation without getting hurt. And secondly, you should never rely completely on technology. It’s a great thing, but technology is only an aid. Sooner or later, technology will let you down if you rely on it blindly. Technology can break, or some data-entry person can enter the wrong information. My advice is to use technology, but correlate it with your own senses to make sure the technology is giving reasonable results. In computer programming, we call these ‘sanity checks’. If I had relied totally on my low RPM warning light to tell me my helicopter had an engine failure, I would have blindly followed my emergency procedures and crashed a perfectly good aircraft into the water. And, both my crew and I could have died as a result. However, I used my own God-given senses to do a ‘sanity check’ of the technology, and I correctly made the decision that the low RPM warning light was wrong. I’m glad I was right.
Flying helicopters was a lot of fun while I was in the Army, but it also had its scary moments. One such time was when I was flying from Fort Polk, Louisiana to New Orleans. I was flying a UH1H (Huey) helicopter along with my copilot and a crew chief. On the north side of New Orleans is Lake Pontchartrain. The lake is 630 square miles in size and is 24 miles across from north to south. To save time when flying to New Orleans, we pilots would often take a ‘shortcut’ across Lake Pontchartrain.
Now the good think about flying the 24 miles across the lake was it saved us 15 to 20 minutes because we didn’t have to fly around the lake and circumvent civilian airfields. We could zip across the lake and land directly at the Louisiana Air National Guard base which was located right on the south shore of Lake Pontchartrain. The civilian air traffic controllers also liked our Army helicopters to fly directly across the lake to the airbase because it meant they didn’t have to worry about us getting in the way of the civilian airliners coming in to land at New Orleans International Airport.
Of course there is a bad side to everything. The bad thing for us was that if our helicopter developed some type of malfunction while we were over the lake, we’d have nowhere to land except in the water since we would be flying at a low altitude. You see, the military had a rule that we could only fly over water in our helicopters if we were high enough to glide to the shoreline if we had an engine failure, or if the crew wore water survival gear. Since it is 12 miles from the middle of Lake Pontchartrain back to the shore line that would mean with a glide ratio for our helicopter of approximately 4 to 1, we could glide about 4 feet for every 1 foot drop of altitude. With 12 miles from the center of the lake to the shore line, we would have had to be flying at a height of about 3 miles (approximately 15,000 feet). That’s doable in a helicopter, but we’d have needed to have oxygen, plus it would have taken extra time to climb that high, and of course we’d have been in the way of the civilian airliners. Suffice it to say, we opted to fly across Lake Pontchartrain at a 1000 feet while wearing water survival suits.
Anyway, there we were flying fat, dumb, and happy across the lake. And wouldn’t you know it, at about the halfway point when we were 12 miles from the nearest land, our helicopter’s low RPM warning light begins to flash and the corresponding warning alarm sounds over our intercom. Now, the low RPM warning light is designed to let the pilots know when their rotor blade is slowing down. Since the fast spinning of the helicopter’s rotor blade is what keeps the helicopter flying, having it slow down is not a good thing. Normally, having the low RPM warning light come on while you’re flying straight and level means you’re engine has stopped working. And of course, that would be a very bad thing, especially if you’re over water with the nearest land 12 miles away.
Now, you might think having an engine failure in a helicopter means it would just fall out of the sky. But that’s not the case. If the pilot lowers their collective (the control that changes the pitch in the rotor blade) fast enough, the helicopter will still begin to fall (hey, it was going to fall anyway), but with the reduced blade pitch, the air coming up through the rotor blade will keep it spinning. The spinning rotor blades sort of act like a parachute in that it slows the rate of descent, and the pilot can glide forward about 4 feet for every 1 foot of descent.
Note: To any ex-helicopter pilots who might read this story, believe me, I am well aware a variety of factors such as speed can drastically affect the glide ratio, but hey, this story is mainly written for non-helicopter pilots, so please cut me some slack. A 4 to 1 ratio explanation is just used as an average.
Anyway, pilots are trained in emergency procedures for various malfunctions such as an engine failure. Now, initiating the emergency procedure for an engine failure needs to be done quickly. If the helicopter engine stops and the collective is not lowered quickly enough (I’m talking a couple of seconds), the air resistance against the rotor blade will slow it down so much the pilot will never get it spinning fast again. Consequently, the pilot has to react quickly.
At the same time, pilots also have it drilled into them that technology can sometimes be wrong. An aircraft’s instruments are an aid, but they aren’t fail proof. In other words, the instrument telling you something is wrong might be wrong itself. That’s why pilots have it drilled into them to combine the warning from the instrument with the pilot’s other senses before making a decision. And, of course, everything has to be done quickly.
So there we were flying at a 1000 feet above the water with 12 miles to the shoreline when the low RPM warning light and alarm comes on telling us our rotor blades were slowing down. I happened to be flying at the time. When the low RPM warning light and alarm came on, one part of my mind had a split second of fear as it envisioned our helicopter crashing into the water of Lake Pontchartrain a 1000 feet below. However, another calmer part of my mind went, ‘Hmm. I did not feel the helicopter twist which should have happened for loss of torque in the case of an engine failure. And, the helicopter did not get quiet. I can still hear the noise of the engine.’ So, I didn’t begin calling “Mayday, mayday” over the radio, and I didn’t initiate an emergency procedure for an engine failure. Instead I told the copilot we had a faulty RPM warning light, and we continued flying the remaining 12 miles across the lake until we landed safely at our destination. Fortunately for us, the Louisiana Air National Guard maintenance personnel at the base were very good, and they had our faulty RPM warning light replaced in short order once we landed.
Moral of the Story: First off, you never know when something bad is going to happen. You can be going along with everything going great when suddenly out of the blue comes a dangerous situation. You can’t live in fear of something bad happening, but with proper training and backup plans (i.e. emergency procedures) you can at least have a fighting chance of getting out of the dangerous situation without getting hurt. And secondly, you should never rely completely on technology. It’s a great thing, but technology is only an aid. Sooner or later, technology will let you down if you rely on it blindly. Technology can break, or some data-entry person can enter the wrong information. My advice is to use technology, but correlate it with your own senses to make sure the technology is giving reasonable results. In computer programming, we call these ‘sanity checks’. If I had relied totally on my low RPM warning light to tell me my helicopter had an engine failure, I would have blindly followed my emergency procedures and crashed a perfectly good aircraft into the water. And, both my crew and I could have died as a result. However, I used my own God-given senses to do a ‘sanity check’ of the technology, and I correctly made the decision that the low RPM warning light was wrong. I’m glad I was right.