The Importance of Density Altitude


Density Altitude:  Pressure Altitude corrected for non-standard temperature.

That’s the book definition of density altitude.  The problem is, that definition leaves a lot of general aviation pilots scratching their heads.  What really is density altitude?

All airplane engines rely on air and fuel mixing together, then that mixture is ignited to create combustion. Normally aspirated piston engine airplanes get their best performance at sea level, where the air is nice and thick, allowing plenty of air molecules to get sucked in the engine intake.  As a normally-aspirated airplane climbs, the ambient air pressure drops with an increase in altitude (the air gets thinner, less dense), thereby reducing airplane takeoff, climb, and landing performance.  There just isn’t as much air at higher altitudes, to put it simply.

Turbo charged piston engines assist with this air density problem.  A turbo charger boosts the air coming into the engine and fools the engine into thinking it is at sea level pressure all the time.  The higher the altitude, the faster the turbo charger spins, spinning the compressor faster, which compresses more air to continue to give the engine sea level pressure air.  This gets faster cruise speeds the higher you go.

Both normally aspirated & turbo charged engines do experience longer takeoff rolls and reduced climb rates at higher airport elevations & higher altitudes.

How does this all relate to density altitude?

When the outside air temperature rises, the air becomes thinner, less dense.  This means that when an airport elevation is 1,000 feet, but the density altitude is reported as 3,000 feet, the airplane engine thinks it is at 3,000 feet.  It won’t accelerate as fast.  The airplane’s climb rate will also be reduced.  That means that the normal climb pitch attitude a pilot is used to seeing won’t be accurate at higher density altitudes. It will lead to slower indicated airspeeds, slow enough to potentially lead to a stall if a pilot isn’t paying attention.

Where does this get dangerous?  High elevation airports.  Whenever the OAT creeps above 85 or 90 at an airport that is higher elevation (I would classify higher elevation as 2,500 feet or higher), the corresponding density altitude sky rockets.  If a pilot isn’t paying attention to airspeed or angle of attack (if the airplane is equipped with an AOA), a stall can come very quickly on climb out.

What to take home from this?  Monitor your climb speed and angle of attack, especially right after takeoff, when you hear density altitude on the ATIS or AWOS.

Building An Airplane


Randy Vanstory, a long-time customer of Texas Top Aviation, decided in early 2017 to build his own airplane. Randy currently owns a Mooney M20J and has been active in aviation for a number of years.  He took on the Vans RV 10, starting in February 2017.  He’s about halfway through right now, with an estimated completion of mid-2020.

A completed Vans RV 10

I asked Randy what gave him the desire to build his own plane.  “I love building things, learning new things, and working on things” he said.  “This satisfies those desires all in one project.”  Randy had a desire to work with his hands, to create something of his own, and building an airplane put several of his passions together in one project.

Lots of pilots out there dream of building their own airplane in their garage.  There is a certain cool factor to putting together an RV or a Lancair in a garage, then trucking it out to an airport, attaching the wings, then flying a personal creation for the first time.  An airplane unique to you, since there isn’t one quite like it any where else.

That’s the beauty of a homebuilt.

Here is a link to Randy’s build video done by Kobalt Tools.

BendixKing Throws It’s Hat in the Glass Panel Ring

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Two pilots walk into an FBO.  “Nice airplane,” Pilot 1 says to Pilot 2.  “What kind of panel do you have in it?”

“I just went all glass,” Pilot 2 says.  “Put in the Garmin G500 TXi, a GTN 750, and upgraded to the GFC 600 Autopilot.  Even put in the Mid-Continent standby instruments.  It’s a pretty sweet set up.  What about you?”

“Wow, sounds like it!” Pilot 1 responds.  “I went a different route.  I liked all my old BendixKing instruments, so I stuck with the company.  I put in a BendixKing AeroVue Touch panel, a BendixKing KSN 770 touch screen GPS, kept my KFC 225 autopilot, got the ADS-B out compliant BendixKing KT 74 transponder, and finished it off with a King AeroFlight KI 300 Digital Backup instrument.”

Wait, what?  BendixKing?

Yes, my friends, BendixKing is still around.

We are all used to the latest and greatest Garmin products these days.  Don’t get me wrong, Garmin and Aspen make great retro-fit products for your instrument panel, while Garmin and Avidyne are at the top of the touch-screen GPS market, but don’t forget about BendixKing.  They are staying in the game too.

BendixKing announced in April the xVue Touch for experimental aircraft, with the STC for the AeroVue Touch for certified aircraft coming later this summer.  The xVue and AeroVue touch are pretty nifty units, comparable in features to what Garmin is doing with the G500 TXi and G600 TXi.  It will be difficult to claw back into a competitive market share with Garmin, but BendixKing might find a niche market of followers.

Let’s take a look at the unit.

BendixKing AeroVue Touch

Now, I have not used the BendixKing AeroVue Touch or the xVue Touch, only read about them.  But, what I’ve read sounds pretty cool.  The display has really good resolution (BendixKing brags it is the highest screen resolution available), synthetic vision that comes standard (Garmin & Aspen charge extra for synthetic vision), plus VFR Sectional Charts & IFR High and Low Enroute charts, making paper charts even more obsolete.

The display is 10.1 inches and can be easily swapped between a full screen instrument mode or a split screen setup as seen above.  Apparently, BendixKing has 3-D moving maps available on the AeroVue Touch too, which is standard.

The one thing Garmin has on the BendixKing AeroVue Touch right now is engine information.  The G500TXi has a full complement of engine gauges available; the AeroVue Touch doesn’t, yet.  BendixKing says it’s in the works, as well as radio information and autopilot control.  I’m assuming the future autopilot control software would mean you could remotely mount an autopilot controller and input all functions from the AeroVue Touch display.  The nice thing about these future upgrades is all the software updates are free through BendixKing.

The sticker price for the forthcoming unit is going to be about $12,600.  Garmin’s 10.5 inch G500 TXi is $16,000, while Aspen doesn’t offer anything quite that big.

BendixKing KSN 770

I’ve been keeping my eye on the BendixKing KSN 770 Touchscreen WAAS GPS for a few years now.  It never really has caught on quite like the Garmin GTN 750 or the Avidyne IFD 540.  BendixKing took the same route that Avidyne did in creating a hybrid touch GPS (or mini-MFD if you want to look at it that way) where a pilot can perform functions either using the touch screen or utilizing soft keys on the edges.  I like the hybrid touch approach as I have been bounced around in turbulence while trying to tap something into a Garmin GTN 750 and it can prove difficult.

Similar to the AeroVue Touch, BendixKing utilized split screen technology in the KSN 770.  It’s a full WAAS unit that is already certified.  It’s sticker price is $14,200, compared to the Garmin GTN 750 at $17,200 and the Avidyne IFD 540 at $15,000.

Other BendixKing Gadgets

Here are some other BendixKing Gadgets both available now and in the works:

Is The Approach Active? Flying Garmin Instrument Approaches Seminar


Hank Gibson from Texas Top Aviation will be presenting a seminar on flying Garmin instrument approaches with the different Garmin GPS units.  Whether you have a Garmin 530/430 unit, a Garmin GTN 750/650 unit, or a Garmin G1000, all will be discussed.  You’ll walk away with some tips and tricks, plus a better understanding of your Garmin unit.

WINGs credit will be given for attending.  The seminar is hosted by Redbird Skyport at the San Marcos Airport (KHYI) in Redbird’s large conference room.  The seminar will begin at 10am on Saturday, June 30th, 2018.

It’s always quicker to fly than drive and Redbird has plenty of ramp space to accommodate seminar attendees.

Registration is required.  Please visit the registration page on  Space is limited to 20 individuals, so please make sure you register if you want to attend.

Garmin GTN 750 Tips & Tricks


The Garmin GTN 750 is an awesome piece of equipment.  Garmin tried to make the user interface with the touch screen as simple as possible (though there still is a bit of a learning curve when moving up from a Garmin 530W).  Garmin also integrated several key features that the 530W did not have that makes flying with a Garmin GTN 750 in IFR all that much better.

The two features of the Garmin GTN 750 I want to focus on today are the “Load Airway” feature and the “Hold at Waypoint” feature.  If a pilot isn’t looking for these specifically, they can actually be a bit hard to find.  The “Load Airway” feature is especially handy when flying IFR long distances with several airways as part of the clearance.  Here’s how to utilize both.

Load Airway

  1. On your flight plan page, insert the waypoint that you will be joining the airway, or, if your clearance was radar vectors to join an airway, then insert the waypoint on the airway that begins the leg you will be joining on.
  2. Tap the waypoint you just inserted.
  3. A menu will pop up.  Tap Load Airway.
  4. Select the Airway you want from the next menu that pops up.
  5. Then, a list of waypoints will display to exit the airway.  Select the waypoint where you will be exiting the airway.
    1. Note:  Garmin defaults to listing these waypoints alphabetically.  If you unselect the “Sort Alpha” option, it will sort the waypoints by direction and distance from the entry waypoint.  This is a little more practical, easier to work with, and how I recommend doing it.  This way you can either scroll up or down depending on the direction of travel on the airway and find your exit waypoint.
  6. Tap Load.
  7. The Airway and all the waypoints in between your entry and exit waypoints appear in your flight plan.
  8. If you are getting vectors to join the airway, you’ll need to use the Activate Leg function to activate the leg you will be joining the airway on.
    1. On the Flight Plan page, tap the waypoint that ends the leg you want to activate.
    2. On the menu that pops up, tap Activate Leg.

Hold At Waypoint

The Garmin GTN 750 allows pilots to place a holding pattern at any waypoint that is in the Nav Database (or any user created waypoint).  Here’s how to do it.

  1. On the Flight Plan page, tap the Waypoint that you want to hold at.
  2. On the menu that pops up, tap Hold At Waypoint
  3. On the next menu that pops up, input either the inbound or outbound course, right or left turns, leg time or distance, and the EFC time, then tap Load.
  4. You will see the hold now as a Waypoint in your flight plan.


Once the hold is entered, the GPS will go into Suspend mode, suspending the Flight Plan Waypoint Sequencing.  Once you are ready to depart the hold, you will have to tap Unsuspend before crossing the holding point on the inbound leg, then the GPS will resume normal waypoint sequencing.

These are 2 of the really cool, gee-wiz features of the Garmin GTN 750.  Following the above steps will make IFR flying much easier for the pilot, as well as much more enjoyable!