News

Breathing…It’s The Difference in Engine Performance

ByJoe Casey November 27, 2018November 27, 2018

The PT6 engine that’s found on the Jetprop and Meridian is designated a -21, -34,-35, or a -42A. The Continental engine on a Malibu is either a TSIO 520 or a 550. What’s the difference? Why should I care? Most pilots don’t understand the difference, but it’s pretty easy to understand…and it’s all about breathing.

Whether a piston or a turbine, the engine has a ratio of fuel/air that works best. For a piston model, we can make adjustments to this ratio by adjusting the mixture. In climb we use a richer ratio to help cool the engine, and in cruise we lean the mixture to save fuel since we don’t need the extra fuel for cooling (due to higher speeds which cools the engine). In the turbine, the ratio is set and there’s nothing that can be done about it…except climb to a higher altitude. But, more about that in a second..let’s go back to the piston discussion…

Piston: A Continental 520 engine and the 550 engine are flown exactly the same. On takeoff, both will develop 310HP (38″MP with the 520, 35.5″MP with the 550). So, why would a pilot want a 550 in his airplane as opposed to a 520? The answer is breathing.

A 520 is named appropriately because the engine displaces 520 cubic inches of air with each complete cycle of all 6 cylinders. To determine the displacement, just figure the bore (diameter of the cylinder) and the Stroke (how far the piston travels in the cylinder) and plug the numbers into this formula:

CID = Bore X Bore X 0.8754 X Stroke X # of Cyl.

Here’s the bore and stroke of the Continental 520 and 550 engine:

TSIO 520: Bore = 5.25″ and Stroke = 4″
TSIO 550: Bore = 5.25″ and Stroke = 4.25″

So, you can see the two engines are exactly the same except the 550 has a little longer stroke, and therefore displaces a little more air. Said another way…it the sucks the air into the engine a little better.

So, with this knowledge, the ability for the engine to breathe becomes a little more clear. Both a 520 and a 550 will perform exactly the same until the point that a 520 simply cannot suck enough air and begins to develop less MP as a result. For most 520 engines, this will happen somewhere around 18,000 ft. But, it is dependent upon a myriad of factors including: health of the engine, altitude, temperature, and atmospheric pressure. When the 520 hits this point, the throttle can be full-forward, but the engine will not develop full MP, but some number that is less. I’ve seen a max MP at FL250 in a 520 Malibu to be about 31″MP. So, you can probably guess that the rate of climb will correspondingly suffer as the engine develops less MP. How do we fix this problem? Enter the 550…

Since the 550 displaces more air, the engine will maintain max MP to a higher altitude. When the 520 begins to develop less power at about FL180, the 550 engine will be able to continue to maintain 35″ at a higher altitude. Make no mistake…the 550 will also hit an altitude where is cannot develop 35″MP, but this altitude will probably be nearly FL220. So, the 550-powered Malibu will reach cruising altitude faster than the 520.

But, at cruise both engines are pulled back to 30″MP. So, either engine will deliver the same cruise speed because they are both able to develop 30″MP at any altitude. Does it really matter if you’ve got a 520 or a 550 engine? Answer: not much. Both are excellent engines and both will deliver the airplane to the destination, but if the chosen altitude is above FL180, the 550-powered airframe will probably arrive a few minutes earlier. Which would I want if I were purchasing an airplane? It’s not a big enough deal, IMHO. I’d select the best airframe/engine/prop combination and not put much weight into the 520 vs. the 550.

Turbine world: So, how about the -21, -34/35, and -42A compare? Here, there’s big difference, but it’s still all about the breathing. A -21, -34/35, and -42A are all derivatives of the famous PT6 family of engines, and all are designed to be 1000+SHP engines de-rated to fit the airframe. For instance, the -42A engine is 750SHP when mounted on a King Air 200, but the same engine is derated to 500SHP when mounted on the Meridian. Ditto with the -21 and -34/35 engines…all are de-rated. So what’s the difference? Breathing…

At the lower altitudes all will develop their maximum rated SHP, meaning they will all develop maximum torque. And, down low there’s plenty of air to breathe so the engine has no problem developing that torque at a low ITT. But, as altitude is gained, the engine must suck more air to develop the same torque, and the ITT goes up. At some point in the climb (depending upon altitude, temperature, pressure, and IAS) the engine will not be able to produce max torque without exceeding Max ITT. At this point, the engine cannot breathe any more (suck in anymore air), and the power (torque) developed falls off. With the -21 engine, the power falls off quite dramatically because the engine simply cannot breathe well. It is a smaller engine and more air cannot be forced into the compressor section. For the rest of the climb the engine is “ITT limited” and the performance will suffer.

The -34/35 engine is a little bigger and will develop maximum power (torque) to a higher altitude. And, when the torque does drop off (as altitude is increased), the rate of decrease is less because it can breathe easier due to it’s larger size. Guess what? The -42A will beat out the others and develop max torque to an even higher altitude. With this decrease in torque available also comes a welcome friend…less fuel burn. Altitude is the friend of any turbine pilot, and he/she will climb to the highest altitude possible to save on fuel.

The end result is the -21 powered Jetprop will cruise at 238 KTAS (in the summer) with a fuel burn of only 28gph. The -34 will have higher torque than the -21 and will develop more SHP and will have a higher cruise (260 KTAS in the summer) with a correspondingly higher fuel burn (32gph). The -42A will be breathing easily at higher altitudes, and will develop the most torque, but with a fuel flow of 39gph. The Meridian (with the -42A) will not out-perform the -34/35 Jetprop in cruise purely because the Meridian is much heavier.

Just remember…fuel flow in a turbine is always commensurate with its ability to breathe and a turbine’s ability to breathe is a function of the engine’s ability to breathe.

With this knowledge…let’s check your understanding. Answer this question: Will a Jetprop cruise faster in the summer or winter? Remember, cold air is more dense than warm air, and an engine will develop power according to it’s ability to suck in air. More air available, more power available. Answer: Winter.

A good analogy: I’m a Cross-fitter (meaning I do crossfit workouts a lot). In the gym we have various workouts that test a person’s ability to perform. Guess who usually does the best? Right…the guy who can breathe the best. A person is nothing more than an engine…we intake air and combine it fuel and burn it to develop energy. In Crossfit, the person with the biggest engine (muscles that can develop power) that can sustain power (good aerobic capability) will win almost every time. The only variables then are genetics (how well-made is the engine), flexibility (you’ve got to be able to get into the position), and skills (there are more efficient movements). A good Crossfitter will work hard on mobility, skill, and try to increase the bodies ability to increase capacity through a tough workout.

To get maximum performance, the pilot cannot change the engines skill or mobility (at least not without an engine change!), but a thorough understanding of the how the engine breathes will help him/her use the power that is available to the fullest.

Joe Casey’s aviation story began in 1990 with his first flight near Nacogdoches, TX in a Cessna 172. From lift-off, Joe knew he would have a lifetime passion flying just about anything that will leave the ground…He was completely hooked.

Along with being an FAA Designated Pilot Examiner (DPE), Joe is an ATP/CFI-AHMG and Commercial Rotorcraft/Glider Pilot in the civilian world and also a UH-60/AH-64 Pilot-in-Command/Instructor/Examiner Pilot in the US Army Reserves. His passion for the last 19 years, however, has been the PA-46 Malibu/Mirage/Matrix/Jetprop/Meridian. Has has amassed over 6,500 hours in various PA-46 airframes and believe it to be one of the finest flying machines available for the serious cross-country pilot with an eye for efficiency.

Now, Joe has flown more than 12,200 hours in just about every imaginable environment. Whether providing initial/recurrent training in the PA-46’s, TBM’s, instructing in NVG’s in a UH-60 Blackhawk, flying the King Air series of airplanes, giving tailwheel endorsements, or taking kids flying for the first time, he simply loves flying machines and the people who fly them.

Determining Pattern Altitude
ByHank Gibson October 23, 2015October 23, 2015

Figuring out the pattern altitude at an airport should be pretty simple, right? But, in this day of helpful technology, most pilots actually get it wrong. How can you always get it right? Well, it just takes about an extra 15 seconds. Here’s how.

John Wayne Airport Traffic Patterns

As outlined in the Aeronautical Information Manual, section 4-3-3, “traffic pattern altitudes for propeller-driven aircraft generally extend from 600 feet to as high as 1,500 feet above the ground.” Further, in the Pilot’s Handbook of Aeronautical Knowledge on page 13-10, it states: “1,000 AGL is recommended pattern altitude unless established otherwise.”

Okay, so for piston driver’s, we’ve got it narrowed down to 1,000 AGL (Above Ground Level for those who don’t like acronyms). But wait! There’s that very important phrase at the end of the last quote: “unless established otherwise.” That means not all airports have traffic pattern altitudes of 1,000 AGL, or else they wouldn’t put that line in there!

How do you find out what the TPA (Traffic Pattern Altitude) is for a certain airport if it’s not 1,000 AGL? Great question! Your first guess is probably to look on Foreflight. Though this is a good start, it is not the full answer.

Let’s use an example. Look up KAQO, the Llano Airport on Foreflight. At the top of the page, the airport elevation is stated as 1,101′ MSL and the pattern altitude is stated as 1,902′ MSL. From what we just learned, 1,902′ MSL is not 1,000 AGL, so is 1,902′ MSL otherwise established?

On the Airports page with KAQO pulled up, tap the A/FD tab, second to last on the left. Scroll down to Llano Muni. Read the whole entry. Does it state in the entry that pattern altitude is different than 1,000 AGL? It sure doesn’t. So, because it is not otherwise established, pattern altitude at KAQO is 2,102′ MSL not 1,902′ MSL.

Where did Foreflight get that? I have no idea. Too often, though, pilots look at the Foreflight pattern altitude and don’t actually check the Airport Facilities Directory (A/FD). Then, they get the pattern altitude wrong.

What does it look like when pattern altitude is otherwise established? Look up KSGR, Sugar Land Regional, on your Foreflight app. Foreflight states the elevation as 82′ MSL and the Pattern Altitude as 1,000′ MSL. Is this correct? Well, tap that A/FD button again and let’s find out.

On the second line of the A/FD entry, it says TPA-See Remarks. Down in the remarks section, we find the following:

TPA-1000 (918) single engine piston acft, TPA-1500 (1418) for twin and turbojet acft, TPA-500 (418) for helicopters within 2NM.

Foreflight got it right this time for single engine pistons, but if you are in a twin, the pattern altitude is different. What’s the lesson here? Always check the A/FD and don’t always go by what Foreflight says. The A/FD is always right and usually has a little more detail to help set you straight.

One last thing. Both the AIM and the Pilot’s Handbook of Aeronautical Knowledge, when talking about pattern altitude, state, “When operating at an airport, traffic pattern altitudes should be maintained unless otherwise required by the applicable distance from cloud criteria in…section 91.155.” 91.155 defines basic VFR weather minimums. So, to fully interpret what the AIM is saying, we have to take into account the type of airspace we are in to determine if we can safely and legally operate at pattern altitude at a particular airport.

For example, let’s say we are at KCVB, the Castroville Airport. Pattern altitude there is 1,602 feet, which is 829 AGL. CVB is Class G airspace up to 700 AGL, then Class E above that. Let’s say there is a 700 AGL broken cloud layer. Pattern altitude is 829 AGL, so you won’t be able to get up that high with a broken ceiling. What altitude can you do pattern work at to stay legal?

Class G VFR weather minimums during the day below 1,200 AGL is 1 SM visibility and clear of clouds. So, legally, you could fly at 699 AGL (which at CVB would be 1,472 MSL) while in the pattern and be legal. Safe? Maybe, but probably not if you are skimming the base of the clouds. Is 1300 MSL a safer pattern altitude in this example? Well, that is 527 AGL, so probably not, since towers tend to stick up that high sometimes.

Let’s go back to KSGR and put a 1,000 AGL overcast ceiling there. SGR is Class D airspace and we already determined pattern altitude there was 1,000 MSL for piston singles. VFR visibility and cloud clearance requirements in Class D airspace are 1,000 feet above clouds, 500 feet below clouds, and 2,000 feet horizontally from the clouds with 3 SM visibility. In order to stay 500 feet below the clouds, you would be flying a 582 MSL pattern. Safe? Probably not, though it is legal.

To summarize, don’t take Foreflight’s word for pattern altitude. Cross reference the A/FD (it only takes 15 seconds at the most) to verify. If it’s cloudy, it’s really best to stay on the ground, but if you want to find out your legal pattern altitude with a cloud deck, cross reference 91.155. I don’t recommend flying below pattern altitude because it is there for a reason.
Calm Wind Landings
ByHank Gibson December 11, 2015December 21, 2015

Some of a pilot’s favorite words are heard on the ATIS: “Winds, Calm.” These words set off all sorts of happy bells and hallelujah choruses. Most pilots spend their lives fighting the winds. On those rare days when the winds are calm, great happiness ensues.

But, are calm wind landings more complicated then everyone thinks? Well, they can be if the proper planning doesn’t go into them.

Let’s think about wind. We have surface wind and we have winds aloft. Sometimes the surface winds are calm. When this happens, certain airports have preferred calm wind runways which are supposed to be used in these conditions. Winds aloft are almost never calm. 95% of the time, there is some kind of wind even 100-200 feet above the surface.

Here is the question pilot’s face when coming into an airport with calm winds: which runway do I use? Do I use the calm wind runway? Do I use the runway that is easiest to enter the pattern for? Do I use the one with the shortest taxi?

A lot of technologically advanced aircraft have a wind indicator on the PFD. This tool is often forgotten in calm surface wind conditions. On the contrary, this is probably the most important tool a pilot can have when figuring out which runway to use when the winds are reported calm.

Here’s why. That wind indicator is showing the pilot what the winds aloft are. The winds aloft should determine what runway is going to be used. If the wind indicator is depicting a south wind, then a south runway should be used. Even if it is a 5 knot wind at pattern altitude, it’ll still be a headwind coming in on final approach. If the north facing runway is used, that same 5 knot headwind can blow an airplane halfway down the runway before the ground speed drops off enough for it to land.

So, the next time you are coming into an airport and the winds are reported calm, take a look at your wind indicator on your PFD when deciding which runway to use. It’ll probably save a few go arounds!
Texas Top Aviation Now Offers Piper PA46 Training
ByHank Gibson August 15, 2017July 14, 2026

Texas Top Aviation is proud to announce that we now offer Piper PA46 Training in the Malibu and Mirage. Our Piper PA46 training is provided with the same excellent & professional approach that has become our hallmark.

The four-day format of this course allows time to answer all of your questions about your new airplane. The Texas Top Aviation Piper PA46 training course leaves you with a confidence and understanding that will help you enjoy your Malibu or Mirage even more.

New avionics have you scratching your head in confusion? No problem. Texas Top Aviation is well versed in the latest Garmin and glass panel instrumentation.

If you are in need of recurrent training in your PA-46, Texas Top Aviation would be proud to help with that as well. Consider us your one stop shop for Piper PA-46 training.

For more information, check out our Piper Malibu/Mirage Training page.

Contact us today to schedule your Piper PA46 Training!
Rudder Use
ByHank Gibson September 15, 2021October 19, 2021

I have the blessing (same say it’s a curse) of being a tailwheel pilot. I did my tailwheel training in a Citabria and have gathered about 400 hours over the years in Citabrias, Super Cubs, and Maules (don’t judge all tailwheel airplanes by a Maule, by the way. The Maule is it’s own unique animal). The blessing of being a tailwheel pilot is that it greatly enhances my stick and rudder skills for all airplanes.

No matter what airplane you fly, basic stick and rudder skills are always important. At some point during a flight, the rudder will need to be used, even if you have an airplane that has a yaw damper. Rudder use is vitally important in the takeoff and landing phase, especially if you fly an airplane that generates a lot of torque on the takeoff roll. Rudder in that phase of flight is pretty evident, because if the rudder isn’t used, you’ll go off the left side of the runway.

Where I want to focus is rudder use in the landing phase. As an airplane comes down final, there are several forces that are be acting on the airplane. When it’s bumpy, updrafts and downdrafts are moving the plane up and down and all around. To correct for a bump that sends the airplane into a roll, aileron is added in the opposite direction of the roll. That aileron input also induces adverse yaw, pulling the nose of the airplane in the opposite direction that the pilot is moving the ailerons.

If a pilot isn’t using his feet correctly, then the nose of the airplane will wallow around through the air as aileron inputs are used. The tail is also moving around quite a bit, so the pilot might not “feel” the yawing moment, but the passengers in the back seat certainly will.

The other advantage that comes with proper rudder usage on short final is the airplane is more responsive to control inputs. When utilizing both the ailerons and the rudder, a pilot is able to fly the airplane much more precisely and control it much better.

This doesn’t mean you have to be staring at the turn coordinator the whole time down final. In fact, that’s exactly what you don’t want to do. Your eyes need to be outside the airplane. Just get in the habit of stepping on the rudder whenever you move the ailerons on final and eventually, you will feel what your airplane is doing. Don’t step on the rudder as hard as you can, but slight pedal pressure in the direction of aileron input will make a big difference.

Rudder is also vitally important for landing in a crosswind no matter that airplane. Crosswind landings are a learned skill that take a lot of practice to perfect. There is also a lot of confusion as to what control input does what during the landing.

Here is the simplest way to picture a crosswind landing and what the controls do:
- Aileron-When performing a crosswind landing, the ailerons keep the airplane over the centerline. If the airplane is drifting to the right of the centerline, add left aileron to bring it back to centerline, then keep enough aileron control pressure in to keep the airplane over centerline. In a perfect crosswind landing, the main tire on the windward side will touch down first. Left crosswind means left tire touching first.
- Rudder-When performing a crosswind landing, the job of the rudder is to straighten the nose to point down the runway. You will not be coordinated in a crosswind landing, you will be slipping, which is the goal. So, with a left crosswind, you will be inputting left aileron to remain over the centerline and you will also need right rudder to straighten the nose. This also prevents the airplane from actually rolling in the direction of the aileron input.
If you remember for a crosswind landing: “Aileron into the wind to stay over centerline, opposite rudder to straighten the nose.” Too much aileron and the plane will drift into the wind. Too much rudder and the nose will yaw in the opposite direction.

Rudder is very important, even in our day and age where a lot of general aviation airplanes have yaw dampers. Our feet only have a job for a short period of time, but that is the most critical time. An excellent way to get more proficient in rudder use is to go get a tailwheel endorsement. If you are in the central Texas area, check out TacAreo in Fredericksburg, T82.

Don’t let your feet fall asleep!
Dry Motoring a PT6
ByHank Gibson March 18, 2021November 24, 2022

When it comes to turboprop engines, a hot start is a really bad thing. For you piston drivers out there thinking, “What’s the big deal, you are just starting a hot engine,” then here’s a little education for you.

In a PT6 turboprop engine, there is a very important temperature gauge that a pilot monitors very closely during each and every start. It is called the Inter-Turbine Temperature gauge, or ITT. This temperature is a measurement of the exhaust gases between the compressor turbine and the power turbine (s). In the picture below, the probe is located where the blue and red colors meet.

In a turboprop engine, specifically the Pratt & Whitney PT-6 in all it’s different sizes and variations, there will always be a specific temperature that the pilot will want to keep the ITT below. This article will deal specifically with a Piper Meridian.

A Piper Meridian starts hotter than almost any other PT6 engine because of the way it’s air intake is designed. Unlike other turboprops, the Meridian has a permanently open inertial separator. This means that not all the intake air makes it to the engine during start because some of it goes out the inertial separator opening. So, coming to a Meridian from operating other turboprop engines can lead to a little bit of a surprise on the ITT temperature being higher than what a pilot is used to when starting.

As a rule of thumb, when starting a Meridian, never let a start continue when the ITT hits 875 degrees. Based on the chart below, you are still in the safe zone at 875 and have about a 50 degree buffer before you have to start getting worried.

On cold starts with a good battery or a GPU, 875 is typically not an issue. Most starts when cold are going to be in the high 700s or low 800s. On a cold start, if you are seeing starts in the mid to upper 800s, try starting with a GPU and see if that lowers the start temperature. If it does, then that means your battery is weak and needs to be replaced. Another tell-tale sign of a weak batter is the Ng doesn’t spool up properly (meaning it settles around 12-13%) or takes a really long time to spool up. Also, never start on the battery with less than 24 volts.

When there are multiple flights in one day, the pilot has to take into consideration the warm engine prior to starting. If the ITT, prior to the start sequence, is above 150 degrees, it is time to do some motoring of the engine.

What is motoring? It is simply using the starter to turn the engine, which leads to air being sucked into the engine allowing the engine to cool off prior to start. The theory is, the cooler your engine prior to start, the cooler the ITT peaks at during start.

Here’s the steps on how to dry motor a Piper Meridian:
- Battery on
- Strobes on
- Fuel Pumps and Ignition off
- Throttle idle
- Condition Lever feather/cutoff
- Push the start button
- Monitor the ITT temperature
- Reaching 150 degrees, if less than 30 seconds have elapsed:
  - Fuel Pumps on
  - Ignition On
  - Condition Lever run
- Reaching 150 degrees, if 30 seconds have elapsed:
  - Push Manual/Stop button to stop the start
  - Let starter rest for 30 seconds
The starter has a 30 second limit on the Meridian, followed by a 30 second rest period. You can do the sequence twice, then, after the 3rd start, there is a 30 minute rest period. Typically, if the ITT won’t cool down to 150 after the 3rd time, there is probably something wrong.

The most important thing a pilot can remember is never, ever push the condition lever forward if the ITT is above 150 degrees. You’ll be well on your way to avoiding hot starts that way.
A Complex Clearance?
ByHank Gibson August 25, 2017August 29, 2017

I was flying in the Rio Grande Valley in south Texas a few weeks ago and heard an IFR clearance given to a King Air that pricked my ears up. It was a clearance from CRP to LRD, but the routing was one you don’t hear too often anymore. Because of active military airspace, the routing was via a radial and DME off the CRP VOR (so a point defined by the radial and DME) to another radial and DME point off the LRD VOR.

It took me a second to think about how to do this the easiest (without setting up the VOR and watching the DME). After a moment’s thought, it’s actually a snap with the G1000. You create 2 user waypoints, one for each Radial/DME spot, then put those 2 user waypoints in your Flight Plan.

Here’s how.

Step 1

Using the big knob, go to the Waypoint chapter. Once there, scroll down to the User Waypoint page using the small knob.

Step 2

Press the New soft key. If you want to name the waypoint something specific, you can do that at the top of the page. If not, it will default to something like VOR 1 or VOR 2.

Step 3

Under Waypoint Type, use the small knob to select RAD/DIS (stands for Radial/Distance).

Step 4

Under Reference Waypoints, again using the small knob (or your keypad), type or dial in the VOR identifier, the radial from that VOR, and the DME distance. Press enter and you are done.

Once you have both User Waypoints created, then just put them in your flight plan (if you forget what you named them, you can just go back to the User Waypoint page), and off you go.