Monday, September 19, 2011

Fuel planning Over The Gulf

Last weekend was a perfect example of why you must "get good" at flight planning while enroute.

I planned a simple direct flight over the gulf at 16000 FT from Tampa, FL to Galveston, TX.

Conventional wisdom says you do your flight planning on the ground and then simply execute in the cockpit.  It sounds simple ... But that rarely seems to work for me.  There are frequently "surprises" enroute that I never seem to be able to predict in advance.

The flight planning on the ground looked quite promising.  The weather was clear and the winds aloft were quite tame along the route (210@10kts)  According to my calculations, the flight should have taken 4hours 9 mins.  This would allow me to land with comfortably more than 1 hour and 51 minutes of fuel to spare, which is about 30 gallons.

Since the weather and fuel looked good, I began my usual preflight.  However, because  this was a flight over the Gulf of Mexico, I took a couple of extra precautions.  First, I made sure my lifejacket was within easy reach. Second, I made sure my Personal locator beacon (PLB) was in my pocket and ready to go.

Shortly after takeoff, things started to change.  Tampa approach was dealing with a lot of traffic in the class B. As a result, my clearance was a bit inconvenient with a heading of 090, followed by several painfully slow heading changes before I was heading westbound. After I leveled off @ 16k FT, I rechecked the fuel projections on R9 and found it predicting 25 gals @ destination.

No problem... (My personal minimum is anything greater than 20) ... So far so good ...

Then Miami center said the dreaded words "We have an amendment to your routing, advise when ready to copy".

Uggg... The new routing was direct Seminole (SZW), direct Crestview (CEW) direct destination.

After refreshing the fuel calcs in the R9, it showed 19gals @ destination... This was not good! I have read so many accident/incident reports where pilots "stretched" personal minimums only to realize later that this was part of the accident chain.

I decided if it didn't improve above 20 by 1 hour from destination, I would divert.  But I still had plenty of time.  In the meantime, I reduced power to 65% to try to conserve fuel.

After about 20 mins, I found myself in and out of a thin cloud deck and facing increased headwinds (240@33).  No immediate danger... But fuel status was now getting worse and the R9 was now predicting 14 gals @ destination.

So I pulled up Foreflight on the iPad and started looking for a place to divert in Louisiana. In addition, I reduced power further to 60% to conserve even more fuel.

I also tried to be clever and "use ATC's help" to conserve fuel.  Every time I got handed off to a new ATC controller, I asked for "a shortcut of 10 to 20 degrees.  This worked remarkably well.  Before I knew it, the R9 was predicting 21 gals@ destination!

But my optimism was short-lived.  The headwinds picked up to 244@42kts.

Now the R9 showed 18 gals @ destination :-(

That did it, time to divert... Houma,Louisiana looked like a good spot.  I told myself 50 miles from Houma would be the decision point to change my IFR flight and start a descent.

Miraculously the winds died down before then and I was able to press on to my destination.

When I landed in Galveston, the R9 reported 20.7 gallons remaining! phew!!

I parked right next to a beautiful Citation CJ2 and a friendly lineman, named Eric, rolled out the red carpet for me!

After a wonderful flight, I am more convinced than ever, that flight planning enroute is an even more important skill than planning on the ground.

Thank goodness that there are cockpit gadgets that let us do that!

Unfortunately, with all the fretting over fuel, I forgot to take pictures!!

(Have to make up for that on my next flight)

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