Is it legal to fly the localizer approach when cleared for the ILS?

Question

Most ILS approaches include localizer minimums that can be used if the glideslope transmitter or receiver fails. For example:

In this case, to fly the ILS you would intercept the glideslope just before PRAIZ and fly the 3 degree glideslope down to minimums.

If we were cleared for the ILS approach, but we instead wanted to ignore the glideslope and fly the LOC only approach¹ (for whatever reason: training, practice, etc.), could we do that without specific ATC approval since it is on the same chart and says "ILS or LOC"?

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¹ We could fly the LOC only approach by crossing PRAIZ at 2,200 ft. and then descend at an "optimum" rate until leveling off at the MDA of 520 ft.

Answer 1

The question really boils down to: "ATC clears me to fly an approach. Is the approach clearance defined by what is on the approach plate, or is it specific to the type of navigation equipment used?" It turns out that it is based on the approach plate.

The answer is found here: https://www.faa.gov/air_traffic/publications/atpubs/aim/aim0504.html Section 5-4-5.a.3(a)

More than one navigational system separated by the word “or” indicates either type of equipment may be used to execute the final approach (e.g., VOR or GPS RWY 15).

When the chart is written as in your example, you are cleared for the approach, and you must use one of the approved types of navigational equipment to fly it. There is no requirement in FAR/AIM to tell approach control which equipment you will be using (beyond the equipment code in your flight plan).

As further corroboration, section 5-4-7.d in the above document specifies that ATC is allowed to clear you for an approach even if the equipment required for some types of navigation systems is not available. This actually is not that rare because NDB/GPS approaches are still used even if the NDB is not working.

The requirement to notify ATC in the event of navigation radio failure is separate. Oddly, you don't have to tell ATC if you have a glideslope receiver at all, but you are supposed to tell them if one that you do have breaks. If it happened while you were actually flying the approach, I would encourage you to execute a missed approach. But if you just want to fly an ILS/LOC approach as localizer-only for practice, ATC doesn't care and you don't need to tell them.

Answer 2

Practically, you could likely do it and ATC would not notice; however, you are not technically adhering to the ATC clearance as it was provided to you and as you read back.

§91.123 Compliance with ATC clearances and instructions.

(a) When an ATC clearance has been obtained, no pilot in command may deviate from that clearance unless an amended clearance is obtained, an emergency exists, or the deviation is in response to a traffic alert and collision avoidance system resolution advisory.

Answer 3

That's even very common when doing flight training, but instead of going to Exec I would sugest yo to shoot a real LOC (only) approach in Pompano just north of it ;)

I can't offer you the 100% legal, floorless, perfect answer for this but ther has been no trouble, yet. Probably the most correct option you have is to particularly ask for the LOC APCH for flight training, but if you demonstrate good airmen ship flying the approch, following a predetermined descend profile leveling off half a mile prior to your DTL, this sould even keep you within half scale until leveling off at yor MDA.

It doesn't matter on which plate the approach is printed, the key point for ATC is, that you are following the same lateral and approximately the same vertical profile, at pretty much the same speed. Ther is obviously no other technique to maintain seperation required.

Obviously you should not plan on doing this without one crew member having the runway inside, or at least with a cloud base reported well above your LOC minimums. If you fail your glide path indicator (put a sticker on it) and you are - for any reason - not visual with the runway at your minimums passing the DTL go around, do not change back to the ILS.