Pilots of piston airplanes wonder what it’s like to fly a jet. Do I need different pilot skills? What are the sensations? Just what is it that makes jet flying different from piston powered airplanes?
So Much More Power
I believe what surprises, and impresses, piston airplane pilots the most in a jet is just how much more power is available.
Raise the nose in a piston airplane and it will climb, at least for awhile. But in a jet with the nose up more than you’ve likely ever seen in normal piston airplane flying, the jet is not only climbing, it’s accelerating. In fact, if you are assigned an initial low altitude after takeoff in a jet you often need to quickly pull the power back to near idle to level off without accelerating through the airport traffic area speed limit.
The fundamental reason jets have so much power is that it is required under the certification rules. Jets must be able to continue to climb at a minimum gradient after an engine fails at the most critical moment during every takeoff.
The deck angle of a jet on takeoff is surprisingly high, because there’s so much power.
That means a twin-engine jet has essentially twice the power required to safely depart for the aircraft weight and atmospheric conditions. If a jet has three or four engines, the rules only require it to meet minimum climb gradient with a single engine failed. That’s why twin engine jets routinely climb quicker than three- or four-engine jets.
These rules don’t apply to the Cirrus Vision Jet because it, obviously, has only a single engine. And they don’t apply to the Eclipse 500 because it was certified in the light airplane category and was not required to, nor did it, demonstrate any climb ability after an engine failure.
Thrust Change Response Time
Jet pilots need more engine management anticipation than when flying a piston airplane because jet engines are slower to accelerate when more thrust is called for, or decelerate when you pull the power back.
It can take from five to seven seconds for a jet engine to accelerate from flight idle to full power. That may not sound like a long time, but just start counting off the seconds as you watch your airspeed deteriorate and the airplane sink. It can be an eternity, and that’s why jet pilots need to be on top of airspeed trends, not just the number shown on the airspeed tape. It’s where your airspeed is headed that matters, not what it is right now.
Many jet engines have higher idle speeds in flight than on the ground so the delay from when the pilot adds power to when the engine spins up to produce it is shortened. Squat switches let the airplane know that it’s on the ground and the jet engines can then reduce to a lower ground idle power so you don’t need to constantly drag the brakes on taxi.
Lots of Drag
The modern jet wing planform is more like a glider than a piston airplane. Jet wings have grown ever longer in span and slender in chord. Just look at photos of an early version of Boeing’s 737 from the 1960s and compare it to current models to see what I mean. And nearly all jets have sprouted tall winglets at the tips to make the wing behave as though it has even greater span.
The reason for the long, “high aspect ratio” wings on jets is to reduce drag at high altitude cruise. In general, and from a purely aerodynamic perspective, the higher the wing aspect ratio, the lower the drag. And low drag means more fuel efficiency, which means greater range, which means shorter runways because you need to carry less fuel for the same trip, and, of course, means lower operating cost.
But jets still need to land, so they need to approach at the lowest reasonable airspeed, and that’s not what those long, slender wings do best. So designers use enormous flaps that track aft to increase wing area tremendously. And those wing flaps extend to pretty extreme angles to increase wing camber. And on most jets wing leading edge devices extend to reshape the airfoil and allow it to produce more lift at lower airspeeds.
Long wings mean big flaps for landing.
All of these devices add lift and reduce stall speed, but at the price of lots of drag. When a jet is configured for landing approach the high drag means airspeed can decay, and a high sink rate develop, very quickly. Combine the higher drag with the slower response from the jet engines, and the piston pilot will discover that energy management—that is to say, airspeed control—is more demanding on every approach.
Numbers Matter More
Any airplane performs best when operated at the target airspeeds, configurations and pitch attitude. But in jets, those numbers matter more than in piston airplane flying.
Establishing the critical numbers happens before every takeoff in a jet. You need to know the takeoff weight first. Then atmospheric conditions such as temperature, airport elevation, wind, runway slope and height of nearby obstructions must all be accounted for.
All of that information leads you to the manuals—thankfully today the manuals are automated—which determines how long your departure runway must be and what the airplane can weigh to clear any obstructions after the assumed engine failure on takeoff. The other critical numbers are indicated airspeed for V1 decision airspeed, Vr for rotation airspeed, and V2 for best engine-out climb gradient airspeed.
Knowing those numbers, and flying precisely to them, assures the jet will have enough pavement available to either abort and stop safely on the runway if an engine fails before V1 airspeed, or climb out clear of obstacles if an engine fails after V1 decision airspeed.
At lower altitudes jets can climb at most any airspeed, but up higher, particularly in the 35,000 to 40,000 feet and above region where jets deliver their best efficiency, very precise control of the target airspeed is essential to climb at all.
And, of course, in the terminal environment there is a minimum airspeed for every phase from clean wing to fully configured for landing.
The final approach airspeed, which is based on landing weight, is called Vref, and is the only airspeed I know of that has a zero tolerance below. Other operating airspeeds are typically plus or minus 10 knots. The rules on Vref are so strict that when flying at that airspeed bank angles are limited to 15 degrees maximum. And if surface winds are gusting, you add some or all of the gust value to create a new, higher Vref minimum approach airspeed.
Jets Don’t Fly Themselves Off
Another important airspeed in jets is Vmcg, which stands for minimum engine-out ground control airspeed.
The reason Vmcg is critical is that an engine could fail before reaching Vr rotation airspeed, but faster than V1 decision speed on takeoff. That means the pilot must be able to keep the jet tracking straight with the engine failed until reaching Vr, the minimum safe airspeed to lift off.
Most jets sit level or even nose-down, to prevent early lift off.
To provide that directional control on the ground, jets sit on their landing gear at a neutral to nose-low angle so even though the airplane is moving fast, the wing isn’t producing lift. Unlike a piston airplane, the jet won’t get “light” on the gear and fly itself off the runway with little or no pull on the flight controls.
To lift off jets take a positive, and in some models very pronounced, pull back on the controls to raise the nose. And in jets with highly swept wings, it can take a few seconds of the airplane accelerating with its nose in the air to create the necessary lift to leave the runway.
It’s also standard procedure in jets to set the flight director command bars to the target pitch angle for best climb gradient with one engine failed. If the worst happens, and an engine fails at a speed faster than V1 decision speed, the pilot it already pitching the proper nose-up angle.
Mach Effects
Finally, a difference piston airplane pilots never think about are the effects of Mach on their airplane. But jet pilots must be aware of Mach and what it can do to affect the handling qualities and performance of their airplane.
Though no civilian jets are now flying supersonically, at higher altitudes all jets experience the effects of Mach. The reason is that air flowing over the wings must accelerate, and though the airplane is moving through the air at a speed below Mach 1, the accelerated air over the wings reaches or exceeds that speed. Engineers call this phenomenon the “local airflow” and that speed is different over all parts of the jet.
When local airflow over the wing reaches sonic value it’s called “critical Mach” and a shock wave over the wing is created. As the shock wave moves over the wing chord it can change the lifting and pitching characteristics of the wing, and not in good ways.
At altitudes near the certified ceiling of a jet the indicated airspeed—the airspeed a wing needs to produce lift—can approach a stall. At the same time Mach effects can be disrupting lift. This is called the “coffin corner” because if a pilot speeds up, Mach effects can make the airplane difficult or impossible to control. If he slows down, the wing can stall.
More recent jet designs have an expanded “coffin corner” that is many knots wide thanks to better aerodynamic understanding, but if a jet pilot attempts to climb too high for his aircraft weight, or the air temperature is too warm, it’s still possible to blunder into a situation where the airplane is buffeting because it’s flying to slow, or too fast, and in the real coffin corner, it’s both too fast and too slow.
Could I Fly a Jet?
The answer is yes. You’ll need a greater understanding the airplane’s performance capabilities, and how its systems function and how to deal with system failures, than in piston airplanes. And you’ll need to be more precise in your flying. Compared to piston airplanes, jets can change airspeed and altitude much more quickly. More precise management of attitude and power are required. Flying jets is an instrument procedure even on the clearest of days because only the flight instruments can provide the precision necessary for altitude, airspeed, and course control.
I hope you get the chance to fly a jet one day. Though not all pilots will find it to be more fun, I know everyone will find it to be more challenging, and probably more rewarding.
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This is a fantastic write-up, especially for the piston pounders like me! Thank you so much!
Nice article. Many years ago I was involved in flight testing a Learjet 55 for an autopilot installation (I designed flight control systems) and I observed the “coffin corner” many times at high altitudes (typically over 47k). Stall and mach buffet where only a few knots apart. Also, many jets need automatic mach trim to counter the pitch down moment that starts ramping with increasing mach. This brings back the positive pitch stability with speed.
Hi Ray,
Interesting that you mention the Mach trim many jets employ. When the MCAS Boeing used to add stick force to the 737Max under certain conditions was blamed for two fatal accidents many outlets claimed it was some sort of novel and unproven technology.
But, as you note, the trim system has been used for decades to compensate for changes in the aerodynamic behavior of a jet. And we pilots were not alarmed, any more than we are frightened of the automatic pitch trim every autopilot uses to fly the airplane. Even though such systems function without pilot input, the human still must understand their design and operation, and how to take command when there is a failure.
Thanks,
Mac Mc
Mac, as a Citation (all) ground school instructor at CAE for 31 years, I argued that new B-737 had experienced an equivalent to a runaway trim and the proceedure for that would have prevented those crashes if recognized and executed by the crew. Your discussion is right on point.
Very informative and interesting article. Thank you.
Hi Mac, my first comment is that once you make the transition to jets, in my opinion they’re easier to fly because there’s much less engine management, and in general a lot more autopilot control. There’s basically the power levers (whoa & go), and usually airbrakes or flight spoilers to aid in slowing down or increasing descent rates. However, as you mentioned, the big difference is the attention paid to precise airspeed control, and flight path control when routinely the pilot has to meet crossing and airspeed restrictions. (autopilot and auto throttles pretty much take care of those variables). I had my eyes opened when transitioning from Hawker jets to the Gulfstream 280 pictured in your column. After flying straight wing Citations for years and then the Hawker series for more years, the 280 was an attention getter for me at high altitudes. We routinely flew the Citations and Hawkers in the high 30’s up to FL 410. The Hawker was a jet you could grow old in–very docile, with a fat wing and only moderate sweep which was good for a maximum cruise of about M.78 (Hawker 900XP). It would land like a big 172. The 280, on the other hand, has a real thin wing, high sweep, and enough power at mid weights to climb on up to FL450 depending on temperature and cruise at M.82. I learned to pay real close attention to the AOA indicator at high altitudes and between that and climb rate I could discern if I was asking the airplane to do too much. It’s been a few years now since I hung up my jet wings, but I seem to remember on the 280 to stop any climb attemps when the AOA approached .65. At cruise of course you would normally see something more reasonable in the .40 – .50 range. It’s been a while so I forger the exact numbers we would typically see. I fly way below the flight levels and high mach regime now in my Stinson 108. I always enjoy your columns–been reading them for years.
Hi Dennis,
You’re right. Power setting in a jet, especially since the perfection of full-authority digital engine controls (FADEC), is a snap compared to a piston engine, or even most turboprops.
The jet engine thrust is controlled by a single lever instead of the three–throttle prop and mixture–common to piston engines. And many jets with FADEC have throttle “detents” for takeoff, climb and cruise so you can advance the lever into the detent without even looking at gauges.
Another jet advantage is something called automatic power reserve (APR). If the engine controls detect loss of thrust in one engine APR automatically increases the thrust from the operating engine to provide a margin of climb gradient to get away from the ground.
And as you say, given the very capable automatic flight control systems found in jets, the jet pilot is often less “busy” than a piston pilot flying in the IFR system.
Mac Mc
Tow other things you might want to cover would be the “coffin corner” or mach buffet, and the handling on take off – not entirely restricted to jets – wherein there is momentary negative lift effect from elevator movements on rotation, in addition to the sweep back effect.
Oooops didn’t read the whole article before posting – you did cover mach buffet.
bad on me
My biggest surprise in transitioning to jets was not the speed or control of the jet (apart from the above mentioned need to pull waaaay back the power for a low altitude level off) – it was the panel, and the modes of the flight director. The Guidance panel has many modes, and to understand them all takes time (experience with a G1000 or similar TAA will help). There are a hundred switches to learn. There are a lot of call outs and procedures to learn pat. My first jet was an Embrear 170, my second a Citation X, both on the higher end of panel and procedural complexity and it was a steep learning curve from a Bonanza and Cessna 310.
Hi Mac,
16 months ago, AT AGE 65 with 7500 single engine hours, and only 21 multi engine hours, I made the exact transition to jets that you described, attending CE-525 Initial at FSI KMCO. The transition for an old piston dog like me was, well… not an easy one. My poor little addled brain just couldn’t keep up with the pace of activities at 400 kt. I made an intermediate step to the PC-12 NG for about 6 months, then hopped back in the CJ2/3. To my immediate relief, I found it easier to stay ahead of the plane. That time spent at 260 kt. had been quite therapeutic, in my case, and eased the transition to jets tremendously. Now that I’m back in the CJ’s, I find myself waxing nostalgic about the wonderful Honeywell Primus Apex in the PC-12. The Uni-1 and the Collins Proline are like working on an old 386 DOS computer, compared to Primus Apex, especially in VNAV capability. I must say though that being able to climb lickety-split to the high 30’s and higher to get above weather is quite gratifying, compared to the 20’s achievable in the Pilatus. My world these days is 450 smooth, and I like it.
Cheers, Drew Kemp
Great article Mac. In my opinion, jets are much easier because of the reasons mentioned in the Comments by Dennis Crenshaw. However, since the time to accelerate from idle to max. power with jet engines is soo long (12 to 14 seconds in my experience), I ALWAYS made the aircraft I was flying as high in drag as possible, so jet engine was well above idle and would accelerate as fast as I moved the throttle…. amen, Amen, AMEN. FYI, during my 50+ years as a pilot, I flew Piper Cub, T-28, T-33, and B-47 aircraft in the US Air Force; T-33, F-84, and F86H aircraft in the Mass. ANG, and owned and flew a Cessna 182 in the civilian sector.
Great article Mac. In my opinion, jets are much easier because for the reasons mentioned in the Comments by Dennis Crenshaw. However, since the time to accelerate from idle to max. power with jet engines is soo long (12 to 14 seconds in my experience), I ALWAYS made the aircraft I was flying as high in drag as possible, so jet engine was well above idle and would accelerate as fast as I moved the throttle…. amen, Amen, AMEN. FYI, during my 50+ years as a pilot, I flew Piper Cub, T-28, T-33, and B-47 aircraft in the US Air Force; T-33, F-84, and F86H aircraft in the Mass. ANG, and owned and flew a Cessna 182 in the civilian sector.
Instrument cross check and situational awareness are also affected by operating at the higher speeds of jet aircraft. Things happen quicker. As an example, a small one degree change in pitch at 400 kts (a moderate jet cruising speed) has significantly higher effect on your VVI compared to 140 Kts. Hence , the resulting airmanship and awareness are more highly tuned. This is especially true in military jet/trainer aircraft where autopilots are not the rule of the day.
Great summary of differences. After flying single engine pistons for 15 years, I had the wonderful opportunity to “fly” an A320 full motion sim. What a difference. Hand flying, after a few landing crashes, I finally made it to the runway. Landings improved after that. Flying by the numbers, watching the trends and knowing the spool up delay were critical. If I got low on short final, it was all over. And, yes, you can easily get behind the plane on climb out. Overall it was loads of fun and a great learning experience.
Hi Mac,
Very informative article on flying jets. I’m still working on my Private. I have read the jet flying flying requirements in the FAA Airplane Flying handbook several times. Your article fills in the blanks and explains subjects that really take more than a paragraph or a page to teach and understand. Actually doing the procedures is the best teacher. Two activities I would like discussed is what the jet pilots in the cockpit are doing before the tractor tows them out of their parking place and during the runup before entering the runway for take-off. Thanks for another great article on flying. Gary
I dunno. The big kahuna is the speed. Otherwise, a prop is much harder to fly than a jet. Lots of power, no torque, climb above weather. Getting your brain on front o the aircraft is the big challenge.
Vinve Massimini Kentmorr Airpark MD (3W3)
Yes agreed…that was going to be my comment also, in addition to the points made in the posted article. You have to think a good 10 minutes ahead of the plane at times which translates to many more miles than going at lower speeds and altitudes. My transition was from multi-engine pistons to a fairly fast B1900D to a 737-200. So the transition was gradual and never felt like a handful to cope with.
I could never figure out why the Elcipse was allowed lower OEI climb requirments than other Part 23 jets, such as the CJ. Any further information?
Hi Bill,
The original Eclipse 500 design intended to meet the same engine-out takeoff climb gradients as all other multi-engine jets. The performance predictions were probably possible, but the empty weight expectations were impossibly low.
When it became clear the Eclipse would miss all of its weight targets, it also was obvious that, with its limited power, the jet could not achieve the required engine-out climb standards.
To save the program Eclipse management petitioned the FAA to be allowed to certify in the light twin category where no engine-out climb minimum performance is required. The maximum takeoff weight limit in that category is 6,000 pounds so for the Eclipse–as with some piston twins–max takeoff weight was set at 5,999 pounds.
At the time FAA leadership was anxious to see a personal jet enter the market. The FAA and industry were preparing for thousands of light jets to blacken the skies and require more FAA infrastructure and thus a higher budget from Congress. So the FAA agreed to the Eclipse certification request.
We all know how the prediction for thousands of light jet production per year turned out. And how the predictions of jet prices for far less than a piston airplane turned out. But at the time thousands upon thousands of pilots–and the FAA–hoped there was magic to be found.
The last time I looked at an Eclipse 500 airplane flight manual (AFM) there was no engine-out climb or performance data. Only takeoff distance and climb performance with all engines operating.
That’s another oddity because in a Baron, or Aztec, or 310, or any other light piston twin, the manuals show engine-out climb performance, and sink rate, when aircraft weight and atmospheric conditions make it impossible for the airplane to climb on one.
Mac Mc