The summer I finished my private pilot license provided many opportunities to fly. I was 18 years old, cutting grass at the Ohio airport where I learned to fly. The airport job only made flying more tempting as it included a discounted rental rate on the flight school airplanes, which I happily took full advantage of.
The 150 I was flying was cheaper than the 172s and cruised 30 knots slower, which made it a perfect ship for building cross country time for my instrument rating. I mostly flew alone and could take full fuel, which gave me 2.5 hours of flying without any weight and balance problems. I usually went on simple out and back flights without refueling. As I gained experience, I gained enough confidence to fly longer trips.
One summer day, I decided to take the airplane to the Clarion airport in Pennsylvania (KAXQ). Clarion was just over 100nm away so flying round trip would be pushing the fuel reserves. I elected to pack a lunch, fly out to AXQ, refuel and eat my lunch, then head back home. I could have flown to an airport with a restaurant on the field but 18-year old me would have to spend money on lunch then and a PB&J proved far cheaper.
A 5,000 foot runway should be enough for a Cessna 150 to take off on, right?
My basic requirements for the airports I went to was that they needed to have a runway. I was building flight time so being able to log a landing at another airport was reason enough to go there. Clarion had a 5003 ft. long runway situated in the rugged terrain just south of Allegheny National Forest, and it seemed within my ability. I had plenty of alternates available should something come up. Clarion also had a VOR nearby and plenty of highways between it and my base to follow which was comforting because I had no GPS.
I enjoyed mostly smooth air at 5,500 feet and the heat of the day had not yet created turbulence by thermals billowing up into thunderstorms, as so commonly happens in the Midwest during the spring and summer. Shortly after passing the state line and venturing into Pennsylvania for the first time, I noticed a slight vibration in the cockpit.
The engine instruments were all in the green so I flew along and didn’t think much of it. I reasoned I was noticing sounds and vibrations that normally existed in the 150, but were more pronounced due to a small headache that had begun. Usually this wasn’t an issue, but I figured I could drink more water for my headache to go away and the amplified irritation would follow suit. The rest of the flight was otherwise uneventful and I went inside to have my lunch and soak up some air-conditioning in the FBO.
When it came time to leave, I fueled up the airplane and headed for home. The runup went smoothly and within a few minutes I was accelerating down the runway. Only I wasn’t. The mighty 150 usually didn’t have an impressive acceleration on takeoff but it felt especially sluggish today. I remember thinking, “This is weird,” and that thought turned to, “I’m not sure I’m going to make it off the runway,” so I aborted the takeoff.
What was going on? I decided to lean the mixture and try another runup to detect any abnormalities with the engine. Mag check was good, carb heat worked fine – “Let’s see what full power does.” I couldn’t get the RPM into the green arc at full power. Not certain if that was normal or not, as I was still new to the plane, I consulted the manual. It said static RPM should be between 2500 and 2600 RPM, which was well into the green arc.
Not sure as to how safe the plane was to fly, I called back to the FBO to talk to a mechanic to diagnose what was going on. Over the phone, the mechanic said the low RPM in the static runup wasn’t an issue because the engine had a fair amount of time and wouldn’t be able to produce book values. The warm summer air would also drive up density altitude so my acceleration should be expectedly sluggish. Since this was aligned with the thinking that my instructor had taught me in regard to fuel burn and other performance numbers, I was satisfied and told him I would take off and fly home.
Having this new information, I was more committed to the second takeoff. I knew the airplane wouldn’t break ground as willingly as normal and I taxied to the very end to make use of all available runway, ran the power up and released the brakes. The airplane accelerated better than before because I had leaned the mixture but still not what I was expecting. I reached 55 knots and climbed into ground effect. By the end of the 5000 foot runway I was 50-100 feet in the air and still struggling to gain altitude at Vy. The vibration from the flight over had returned, too.
A Cessna 150 with a sick engine is not a good performer.
I looked out the window along the hills covered with massive oak trees and other terrain and decided this flight was not worth continuing. I needed to get on the ground now, while I was still able to do it on my own accord rather than a sick engine and gravity taking over as PIC. Not wanting to end up splattered among the maple trees, I flew runway heading for 10-15 seconds before making a left turn back towards the runway. I flew a teardrop shape and landed in the opposite direction on the runway I had just taken off from.
Thank goodness I was alone with no one else in the pattern. I had frightened myself. With my knees shaking and out of breath, I taxied in to shut down on the ramp. Once I collected myself, I called back home to announce that I wasn’t flying back.
Later that afternoon, the flight school sent the mechanic out to look at the plane. After proving to him that the airplane would not make full power, the cowling came off and he began diagnosing the engine’s problems. The pilot who had flown the mechanic started probing the engine with a flat head screw driver. After pushing against a few parts on the engine, he asked the mechanic, “This isn’t supposed to move, is it?” That part was the “smoking gun” the mechanic needed to diagnose what had gone wrong.
Unannounced to me, the intake manifold connecting the carburetor to the number 4 cylinder had separated during cruise on my flight to Clarion and was creating the vibration I had felt. I was able to maintain altitude and descend, but the engine didn’t have the power to take off and climb. This poor engine was down to 3 cylinders because one was not receiving any fuel/air mixture. Later that summer, the mechanic made a few more trips out to Clarion to work on the plane. The cylinder and intake manifold ended up getting replaced and later that summer I flew the plane back without incident.
Up until that point, I thought aborted takeoffs where only for multiengine airplanes and jets. When something isn’t right, it’s good to take others’ advice and get a second opinion, but ultimately the PIC has to make the call. Lesson learned.
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Good article – thank you.
Very few of the pilots I work with do anything to measure acceleration during takeoff. I’m not fond of the “70-50 Rule of Thumb” (achieve 70% of Vr by 50% of the runway) for several reasons, not least that almost nobody really knows where 50% of the runway is at airports other than their home base.
A reliable method for assessing performance is to measure acceleration during takeoff. Note the speed after a given time (for most airplanes, 10 seconds works). For example, ten seconds after opening the throttle, a typical Cherokee or C172 will be at somewhere better than forty knots; an SR22 will be at around 60 knots. There are variables that affect that speed – for example when you start your count, headwind, airplane weight, density altitude. But once you know what ‘normal’ is for your airplane, you have a benchmark number that is useful. If I normally see fifty knots on a day like today, and on this takeoff I’m at thirty after my ten-count during takeoff, something is wrong, and I have plenty of time to abort.
This measure of performance can be important – not just for getting airborne, but for knowing that one has sufficient power to allow for continued safe flight.
How about identifying a taxiway exit that is at somewhere close to 50% of the lenght of the runway? You pass that point, and you haven’t reahed 70% Vr, you abort.
Good article. It brings to mind some points I learned the easy way, by someone else’s hard knocks. Thank God that someone else was my first flight instructor.
1. Mechanics aren’t pilots. Mechanics repair aircraft to airworthiness standards. It’s the pilot’s job to determine whether or not the aircraft is safe to fly. There’s a difference. Those who know that difference live longer.
2. “The runup went smoothly…” A simple mag check isn’t a runup. It’s a mag check. It’s part of the runup, but there’s a lot more to a runup than a mag check.
3. A lot of engineers spent a lot of time developing easy to use performance tables available in the back of every POH. All that work is worthless if we don’t use them.
My very first runup consisted of checking the mags as per the checklist after which I was given a harsh talking to by my CFI/I and former bush pilot. He informed me all I did was verify roughly equivalent performance of the magnetos.
Next, he had me shut down in the hammerhead and set brakes. We sat there as he proceeded to inform me I’d failed to calculate and verify both engine and flight performance and diagnose potential problems on the ground, where they won’t kill me.
“Always hit the performance charts in the POH. That’s why they’re there.” He had me pull the POH from my flight bag and walked me through three flight performance scenarios, including those applicable to that day. The other two could have resulted in serious injury or death had I attempted to take off in those conditions, one of which was just a little hotter and a little heavier than we were that day.
Ever since, I have always computed and checked:
– Takeoff distance
– Landing distance
– Rate of climb
– Peak RPM
– Peak cylinder head temperature (cowling flaps in position appropriate to outside temperature)
The airfield was just south of Sacramento, where temperatures routinely crest 100 deg F during the summer. “Come summer, you, me, and a full tank of gas will NOT clear those trees beyond the runway. They’re 50 feet high and located 500′ beyond the end of the runway. Are we going to clear them today?” When I stupidly shrugged my shoulders, he asked, “What’s your rate of climb at Vy today? How about Vx?” When I still shrugged, he walked me through the calculations, then said, “Now, you do it. Assume the trees are 100 feet high.”
After about 40 minutes, by which time I’d built a makeshift TOLD card (Takeoff and Landing Data), he had me restart the engines, perform a proper runup including peak RPM (mixture set for peak RPM), cylinder head temperature, oil temperature, and THEN, the mag check, followed by a final check of cylinder head and oil temps.
Next came the minimum takeoff distance. Our little airfield had no thousand foot markers. Heck, it wasn’t even a thousand feet long. He said, “You know the computed takeoff distance. Estimate that and tell me where we should be wheels up and what we should do if we’re not there yet.”
That gave me about 200 feet of abort room. Not enough! So we sat in the hammerhead, engines running, as he had me compute both an acceleration timing check as well as an acceleration distance check. The first says you have to be at or beyond the computed airspeed x seconds after brake release, whereas the latter says you need to be at or beyond the computed airspeed by a certain distance. “Then there’s distance remaining, where you can pass both of the first two due to a stiff headwind but still fail to leave the ground. If you don’t make Vr or Vs1 by that point, stop trying. During my next 20 years while flying for the Air Force, we used the same or similar techniques.
The key point to remember is that it’s important to calculate your aircraft’s performance values. Either obtain or create a good TOLD card and use it. The professionals do, so why shouldn’t you? Your life is absolutely worth the extra effort!
Heck of a story and i am glad you survived. I was on the edge of my chair until we were given the diagnosis.
Tyler,
There are a whole bunch of us who logged their early cross country hours in a 150 much as you did, right down to the PB&J. But most of us didn’t suffer a full blown emergency.
Your account reminds me of something an old instructor told me as a kid back in the ’60s. “You’ll be safe in an airplane so long as you don’t do three things: don’t loose control of the airplane; don’t hit anything; and, don’t give up.” You managed all three simultaneously.
Thanks Kim!
How do you “loose” control of an airplane?
Really. Read the NTSB statistics….. spins, icing………stall in IMC.
he is making a grammar joke…. total douche.
Tyler; good story. Since the POH shows the takeoff roll about 1300 feet, you could easily calculate that if you haven’t achieved takeoff 2,000 feet down the runway, something is seriously wrong. I have a 80*F standard day takeoff roll calculated for each of the 5 types of aircraft I fly, and if I’m over that distance by more than 50%, I always abort. For most GA aircraft, if you’re not airborne and climbing well by 2,000 down the runway, it’s time to quit!
There are a couple of old shop-worn bromides that have stood the test of time that maybe should be taped to your knee-pad: (1) if something seems too good to be true, it probably isn’t; and (2) if something doesn’t seem quite right, it probably isn’t! The second one is especially important in aviation! Never get in a hurry with an airplane. Gravity always wins!
All engines with fixed pitch props should be capable of reaching their full static RPM value.
Different for each airplane/engine/prop and is shown in the Type Certificate Data Sheets if not in the POH. Ask your mechanic.
The mechanic in this story was wrong. Old or tired engine should reach full static or it is UNAIRWORTHY. A mandated check at each annual inspection and of interest to each pilot for the reasons shown in the article.
Isn’t it astounding – the lessons you start learning after you pass your check ride and go out into the big world on your own?
Your article is a very good reminder that mechanics are always “optimists” who literally have NO SKIN in a mechanical failure. Unfortunately, pilots are ALWAYS first to arrive at te accident scene, i.e. mechanic optimism puts you & me in a bad place. You summarized that point nicely when you wrote:
“I called back to the FBO to talk to a mechanic to diagnose what was going on. Over the phone, the mechanic said the low RPM in the static runup wasn’t an issue because the engine had a fair amount of time and wouldn’t be able to produce book values. The warm summer air would also drive up density altitude so my acceleration should be expectedly sluggish.”
I’ve experienced one complete engine failure (at night, over rough terrain) and a couple of partial failures because of very bad advice from mechanics. Engines are NOT designed to ‘make metal’. One mechanic returned a CAP airplane to service when “chunks” of ferrous metal were discovered in the filter during a scheduled O.C. Another A&P failed to correctly diagnose repeated fouling of plugs as a defective wiring harness. Yet another failed the “drop it once, drop it TWICE! test”… and installed a recently dropped spark plug in the engine of a Piper Archer (the plug came apart in flight one night resulting in an emergency landing).
I’ve learned to be skeptical hvery skeptical) of advice from any mechanic (or other pilots) to fly any aircraft that has an unresolved — FIXED! — maintenance or performance problem.
It’s important for all to realize as well that Vy at a higher density altitude can be significantly less (and not usually easily found) since Vy decreases and Vx increases as you climb higher…
3-4 knots slower would have definitely helped with the issue and given you a better safety margin.
Similar happened to me. VanNuys airport, same Cessna type, short field take offs with my instructor. Climb out with flaps 60 kts ias both cylinder heads on right bank separated from block. Lots of smoke/vibration (no instruments readable). Because 2 cylinders kept firing was able to execute rtf. Not enough power to taxi after landing. No Fun