Posted by Shooting some practice instrument approaches at Dallas Executive Airport, Texas
My last flight of this business trip was intended to take full advantage of the wide availability of instrument approaches, including plenty of GPS approved ones. There’s never any charge for making an instrument approach in the US, and rarely any landing fees. So once again, I found myself at Dallas Executive airport in the good hands of Slipstream aviation, intending to take advantage of this with a short flight.
Below is their fleet of Grumman AA5 Cheetah’s parked up in the December sunshine. There’s acres of space here.
Slightly different regulations for instrument approaches
Before we took to the air, my instructor Don spent some time talking through the rules for IFR approaches. These are slightly different from those in the UK, and defined in 14 CFR Part 91.175. [If the link doesn’t work, search within the US Government site at ecfr.gov.]
For example, in the US, unless specific airfield regulations modify it, instrument rated pilots can descend to 200 feet above runway threshold, and if they can see the approach lights (sometimes called the rabbit), then can descend down to 100 feet. As long as they see any one of a range of visual markings – PAPIs, runway edge lights, runway threshold markings etc. – then they can land. Implicitly this does mean there is some visual range, because you aren’t allowed to dive bomb the threshold if you spot it only when directly overhead.
We talked through the details of approach plates and Don helped remind me what all the annotations meant. These were all pretty similar to what I’d seen in the UK, with everything marked as altitude above mean sea level. They don’t use QFE or QNH here, just the pressure setting measured in inches of mercury.
As before, Don used Foreflight on his iPad throughout, and didn’t seem to have any paper/printed plates. This ensured these were always up to date and were much easier to carry around.
IFR capable, without either ADF or DME
The Grumman Cheetahs at the school are all equipped with Garmin 430W GPS, and the aircraft we’d be flying had an HSI linked to it. After pre-flighting and starting up, Don showed me how to select and load the approach on the GPS, and setup all the radio frequencies that we’d need. Although fully IFR legal, these aircraft don’t have an ADF (which I believe is still mandatory in the UK because many missed approach procedures still use these older NDBs), or DME (because the GPS is used for that instead).
This setup is good not only for GPS localiser approaches, but also gives vertical glide slope. There are three types of GPS approaches, called LNAV (no vertical glideslope), LVAV-VNAV (also shows a vertical glideslope) and LPV (even more accurate, enabling lower decision heights as good as an ILS). The last two look and feel just like an ILS but are entirely driven by the GPS satellite information, with the LPV supplemented by measured error corrections to make it even more accurate. This system is known as WAAS in the USA, and EGNOS in Europe. The advantage being that no equipment is required at the airport, making them much cheaper to implement and maintain. Unlike the UK, there are many such instrument approaches in use at uncontrolled airports (i.e. those without a tower). UK regulations require not only a towered airport, but full ATC qualified controllers onsite for any instrument approach to be used.
LPV approaches using the Garmin 430W are perhaps better visualised in this YouTube demo video from Sporty’s (which advertises their training DVD which I haven’t seen so am not in a position to recommend or not).
GPS LPV approach to an uncontrolled airport at Mid-Way, Texas
We departed Dallas Executive to the south on runway 17 and (unusually) signed off with Executive tower. As soon as we had climbed to 2,500 feet, we were almost at the initial approach fix for Mid-Way 18 GPS, called WAKDA. Don helped me to activate the GPS LPV approach, and I could see on the screen what route I needed to take and how far it was to that point.
We flew to it at platform height and the HSI operated like an ILS display. As I neared the next waypoint (OMGEE, the Final Approach Fix) I could see the glideslope indicator beginning to move down. Don’s advice was to prepare for final approach (doing what I’d call the downwind checks) at this point.
This involved switching on the fuel pump, landing lights, strobes (if not already on) and checking the seat belts and hatches were secure. Slowing the plane down to an approach speed of 80 knots by pulling back on the throttle (but not using flaps), we began a controlled descent of around 450 to 500 feet per minute. We were well positioned for the glideslope, and I was able to follow this down to 200 feet and then went visual. I’m pleased to say I pulled off a real greaser of a landing, then quickly accelerated and took off again.
Being an uncontrolled airport, we’d listened to the AWOS (Automatic Weather System) beforehand and I had also self-announced my approach and intentions by radio on the CTAF (Common Traffic Advisory Frequency), both before, during and after the landing.
Don explained the SUSP (suspend) button on the GPS which could be used to navigate to the missed approach point, which we would have done for real if we had not been able to see the runway from 200 feet. If I recall correctly, the GPS automatically suspends navigation around decision height and a softkey indicates SUSP. Pressing this resumed navigation, but to the missed approach point.
ILS and circle to land at Executive
With the foggles back on again, we then returned to Executive and requested a practice ILS for runway 31 which was immediately approved. I remain amazed at how concise and straightforward the radio calls can be, and also how easy it is to arrange a practice approach. I simply said something like “Executive, Cheetah 9929 Uniform, 10 miles south west of FUJET (this is the initial approach fix), request practice ILS for runway 31” and immediately got a response “9929 Uniform, ILS runway 31 approved, report at FERMO”, which I read back. FERMO is the subsequent GPS fix on the approach.
Since runway 31 wasn’t the active runway, we’d need to execute a circle to land for runway 17 which doesn’t have an instrument approach.
[The plate above states that an ADF is required for this approach, but that has been removed from later, current versions]. There is a different betweenthe minimum decent height of 620 feet of the non-precision VOR approach compared to a decision height of 500 feet on the precision ILS.
Again, Don showed me how to setup the GPS, this time for an ILS. The VLOC button was used to switch the HSI to take its input from the ILS receiver rather than the GPS. It really didn’t look significantly different to the GPS LPV approach we’d just done, and when flying down the track I was pleased again to be very close on azimuth and glide slope. The circling height is about 500 feet, so we broke off at that point, taking off the foggles, and completing the circle to land visually. Pleased with another really good landing, we departed to the south and Don requested a final approach with full stop landing using the VOR procedure.
VOR approach which went astray
This is where it went horribly wrong. I did not quite get a grasp of twiddling the right knobs on the HSI, and so although the GPS approach was loaded up, I didn’t really understand why the GPS map was showing me off to the right when the HSI had me on the localiser. It seems this was because I hadn’t aligned the HSI with the compass, and possibly not with the runway either. I really wasn’t sure what I needed to do, and think I must have expected the GPS to set that up as well. The difference being that for an ILS or GPS approach, the compass alignment of the HSI is irrelevant and overridden, while for a VOR navigation it’s not.
So we were somewhat off to the right of track, and completed another circle to land – extending downwind at the controllers direction for spacing with another aircraft. He called base, and when I turned onto final I thought I was a little high. The PAPIs were certainly telling me that. But at our final approach speed of 80, we floated down to another good landing and return to base.
Debrief
Fitting in three different types of approach at two different airports, all within less than an hour, and with no landing or approach fees to pay, is so much less hassle than a similar exercise would be in the UK.
Some more boning up on the 430 options is going to be needed before I fully appreciate what all the buttons and modes do, but the ILS-like functionality of a GPS approach is an extremely helpful tool in the pilot’s toolbox. Shame we don’t have many of them in the UK.
I asked Don for his frank opinion of what it might take me to reach FAA Instrument Rating standard. While this did put him on the spot, he believed it wouldn’t take too much (i.e. many flight hours), but wasn’t able to say what paperwork/visas etc might be required. While this is not my current intention, I’m fairly sure I know what’s needed here.
[For the record, I believe the answer is I’d need TSA fingerprinting, an M1 student visa sponsored by the flight school, a personal visit to the US embassy in London and probably a further UK CAA verification letter. I’d also need to ensure I had met all the minimum flight time requirements including a 250NM IFR navigation trip and sit the one written exam (which can be done in the UK), then take the practical test (which includes a tough oral examination). Unlike the UK Instrument Rating, all the hours of dual instrument training I’ve done for the IMC rating would count. I could even do some further preparatory training towards this qualification in the UK, but must have at least 3 hours in the US before the test. While it can be done in a few days, budgeting for anything up to 2 weeks is probably a safer estimate. Mathew Stibbe details the requirements from personal experience.
Another route is to add an ICAO instrument rating gained elsewhere on to your piggyback FAA licence. This is possible with only a single theory exam and doesn’t require visa, TSA or medical. UPDATE: I took this route in 2014 in Las Vegas.]
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