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The Anatomy of a Hot Start

ByHank Gibson January 14, 2021May 24, 2023

Are you one of those pilots who hates fuel stops simply for the fact that the engine doesn’t have time to cool off?  You pump gas into the plane, hit the bathroom, get in the plane and the oil temperature is still up at 160-170 degrees, leading you to have to figure out how to get the plane going again with a hot engine.  For those without proper training, this usually means a lot of jockeying around with the throttle, mixture, and fuel pump to try and get the thing started without flooding it.  After coughing and wheezing several times, the engine finally comes to life, leaving you to only guess what worked and without the knowledge of how to duplicate it.

Let’s take a step back for a minute to see what is actually happening with a hot engine.  Once the engine is shut off, the fuel in the lines leading from the tank to the engine is vaporized, meaning there is more air in the fuel lines than liquid fuel.  In the engine block itself, there is still liquid fuel in the injectors, but only enough for the engine to cough then quit if started.

When a normal priming and starting procedure is performed, too much fuel is forced into the cylinders and the engine becomes flooded.  A flooded engine just means that the stoichiometric ratio is way too rich, meaning there is too much fuel and not enough air.  The prime does the trick of getting the fuel vapor out of the fuel lines, but it shoves too much fuel into the cylinders.  Once the engine is flooded, it’s a waiting game to allow air into the engine to get the mixture right.  All Lycoming powered high performance and turbo charged engines are notoriously easy to flood when hot.

So, what’s the solution?  By taking a step back to see what is actually happening, you can attack the problem from the source, which is the fuel lines.  You need to get the vapor out of the fuel lines and get some liquid fuel in there.  The procedure for this varies based on the make and model of engine, but I’m going to use the example of the Continental IO-550-N that is in a Cirrus SR22.  I found this procedure in the Continental Engine Manual and it works every time.

(Pilots of other airplanes, keep reading.  I have sections below for PA46s, Columbias, and Bonanzas as well )

• Mixture:  Full Lean (this allows fuel in the fuel lines, but prevents it from going past the mixture control into the engine, sending all fuel back to the fuel tank; a small amount of fuel leaks past the mixture control providing prime for the engine)
• Throttle:  Idle
• Low Boost Pump:  Run for 30-60 seconds (see note below)  (15 seconds in the Turbo Cirrus)
• Mixture:  Full Rich
• Throttle:  Open about 1/4 travel (not 1/4″, that won’t be enough)
• Boost Pump:  Off, but have your finger on Low Boost
• Starter:  Crank (engine will turn over a few more times before firing, this is normal)
• At the first indication of start, turn the Low Boost on, increase the throttle to ensure the engine catches,  then adjust the throttle for 1,000 RPM
  • The engine will fire right about the time you start thinking it isn’t going to work

A few notes regarding engine temperatures:

• If the oil temperature is above 150 degrees, a hot start will be required.  If oil temp is close to 200 degrees, run low boost for 60 seconds in a non-turbo.  If oil temp is 175, run low boost for 45 seconds in a non-turbo.  If oil temp is 150, run low boost for 30 seconds in a non-turbo.  Use 15 seconds for all temps above 150 in a Cirrus Turbo.
• If the oil temperature is between 125-150, skip the hot start procedure, don’t prime the engine, leave the boost pump off, and crank the engine, then boost pump on when it starts and slightly increase throttle to make sure the engine catches
• If the oil temperature is between 100-125, skip the hot start, don’t prime the engine, and perform a normal start with the boost pump on
• If the oil temperature is below 100, perform a normal prime and start

Piper Malibu (PA46-310P with Continental Engine)

• Mixture:  Full Lean (this allows fuel in the fuel lines, but prevents it from going past the mixture control into the engine, sending all fuel back to the fuel tank; a small amount of fuel leaks past the mixture control providing prime for the engine)
• Throttle:  Idle
• Low Boost Pump:  Run for 15-30 seconds depending on oil temperature…
  • Greater than 150 degrees: 30 seconds
  • Less than 125-150 degrees:  15 seconds
  • Less than 100-125 degrees, no need to run the Low Boost
  • Perform normal cold start below 100 degrees
• Mixture:  Full Rich
• Throttle:  Open about 1/4 travel (not 1/4″, that won’t be enough)
• Boost Pump:  Off, but have your finger on the Primer Button
• Magnetos:  On
• Starter:  Crank (engine will turn over a few more times before firing, this is normal)
• Engine should fire with the Low Boost Pump off, but…
  • If the engine starts to die, simultaneously increase the throttle a little bit and hit the primer button.
  • Only tap the primer button, don’t hold it as you’ll flood the engine if you hold it At the first indication of start, turn the Low Boost on, increase the throttle to ensure the engine catches,  then adjust the throttle for 1,000 RPM

Piper Mirage & Matrix (PA46-350P and PA46-350T with Lycoming Engine)

• Leave throttle and mixture idle
  • Before you turn the battery on, ensure the mixture is idle cutoff
  • If the mixture is forward and the battery is on, the low boost pump in the fuel tank will start pumping fuel to the engine and quickly flood it
• Ensure Magneto switches are on
• Open throttle 1/4 travel (not 1/4″ as this won’t be enough)
• Crank
• As soon as the engine begins coughing and wheezing (and this is what it will sound like), push the mixture 3/4 of the way forward
• Once the engine has a good solid fire, smoothly and swiftly push the mixture all the way forward
• Reduce throttle
• Note:  The Emergency Boost Pump can be used as part of the hot start technique, but I usually leave it off.
  • Pro to the Emergency Boost Pump is it can help suck more fuel in and purge vapor during the start
  • Con is that if the engine doesn’t start on the first try, you are flooding your motor

Columbia 400

• Throttle and Mixture Idle Cutoff
• Vapor Suppression:  Run for 30-60 seconds.  Reference above temperatures on the non-turbo Cirrus for run times
• Mixture full forward
• Throttle 1″ in
• Prime for 3 seconds, then off
• Crank
• Once engine fires, primer might need to be pushed momentarily to purge excess vapor
  • On Columbia 350s, the throttle should be twisted (or pushed depending on if it’s an Avidyne or Garmin Columbia) in while cranking
  • Be prepared to reduce power once engine fires

Beechcraft 36 Bonanza

• Throttle and Mixture Idle Cutoff
• Low Boost:  Run for 30-60 seconds.  Reference above temperatures on the non-turbo Cirrus for run times
• Mixture full forward
• Throttle open 1″
• High Boost until fuel flow peaks, then off
• Crank
• Once engine fires, Low Boost might need to be engaged momentarily to purge excess vapor

There are other “procedures” for hot starting out there, but most of them involve starting with full throttle, which can lead to the airplane shooting ahead on a ramp or taxi way if the brakes aren’t properly set.  This can lead to high repair costs, so always be cautious.  Figuring out what is happening when the engine is hot will give you a better chance of getting it started right away.

Reading Weather Prog Charts

ByHank Gibson January 27, 2015July 14, 2026

There are a multitude of weather products out there today to assist pilots in preparing for a flight.  Aviationweather.gov is the best source for getting all the information a pilot needs for planning a flight.  Aviationweather.gov is the National Weather Service’s source for all aviation related weather products.  When I teach about weather and weather briefings, I recommend to my students to utilize Aviationweather.gov in the planning stages, but still call the Flight Service Station to get a full fledged weather briefing before takeoff.

When preflight weather planning, one of the best ways to get a picture of what is happening over a broad area is utilizing the Low Level Significant Weather Prog charts.  The Prog chart gives a forecasted 12 and 24 hour picture of what type of weather to expect over the US.  The Prog chart gives the expected flight rules, areas of turbulence, and where the freezing level is located.  If you’re looking at the 4 panel view, the Surface Prog chart shows fronts, pressure areas, and areas of expected precipitation.  That covers just about everything, doesn’t it?

I believe the Prog charts are underutilized in planning.  Foreflight and Garmin Pilot have given easy access to radar pictures, satellite pictures, METARs, TAFs, and several other sources of weather information.  But, a lot of the easy access data you can get from those apps is current data (with the exception of the TAF) while a lot of the forecast data takes some hunting around.  So, products like Prog charts aren’t often utilized.

The other problem arises when pilots know about Prog charts, but don’t know how to read them, then don’t know how to find the legend to decipher the chart, the chart is often set aside and quickly forgotten about just because of a lack of knowledge.  Have no fear, though, as now we will use an example 4 panel Prog chart to decipher the lines and colorations.

Just looking at the Low Level Significant Weather Prog Chart above, it can be a little confusing.  That’s why they make a legend!

Coupling the legend with the chart above, we can determine some things.  First, California, parts of the Pacific Northwest, a small part of southern Arizona, and a good portion of the Midwest and East coast are going to have marginal VFR conditions in the next 12 hours.  Wisconsin, Illinois, a good portion of the Northeast, and a small portion of the Pacific Northwest will suffer IFR from IFR conditions.  There are going to be a good amount of low level turbulence in the northern and eastern parts of the country.  Finally, the freezing level starts at the surface running in a jagged line across the midwest states and curling up into the Northeast.

That’s a good bit of information, isn’t it?  If a pilot is planning a VFR flight into the Northeast tonight, it would probably be best to wait for another day, according to this chart.

Now, to see what is causing the conditions above, we need to look at the Surface Prog Chart.

The green circular areas above show that some form of precipitation is in that area.  The circular dots with the triangle located in Mexico and Baja California are depicting moderate rain showers.  If the triangle was gone, it would just be moderate rain.  In the northeast, all those symbols are showing moderate to heavy snow showers.  Across the plains, we see a lot of high pressure, meaning visibility and nice flying weather.

These charts are invaluable when it comes to flight planning, especially over long distances when the weather could be changing a lot over the period of your flight.  Put them to use the next time you are planning a trip and you’ll learn you have a much better picture of what the weather is doing.

Avidyne IFD 440 Receives Certification

ByHank Gibson July 1, 2015

Avidyne’s plug and play replacement for the Garmin 430, the Avidyne IFD 440, finally received certification from the FAA last week.  The touch screen GPS unit is being marketed as a simple swap out for the Garmin 430.  This release follows up Avidyne’s release last year of the IFD 540, also a plug and play replacement, but for the Garmin 530.

The features and touch screen of the GPS units sound quite nifty, but it will be hard for Avidyne to compete with the GTN 750 and 650 from Garmin.  The unit prices for the IFD 540 and 440 will be less (and installation is simpler), but we will see how the company does.

The STC allows for installation in 1,000 makes and models of aircraft, according to the company, so there are a lot of possibilities for installs.

In conjunction, Avidyne also released a new version of it’s software for both GPS units.  According to Avidyne, this will unlock multiple features that enhances the capabilities of both units.

To read more on the IFD 440 and it’s bigger brother, the IFD 540, check out Avidyne’s website.