Flap Failure on ILS
 

If you were being vectored onto the ILS and your flaps failed; requiring a no-flap landing, would you notify the tower? (and/or approach?)

Why or why not?

Fly the airplane first and then it's always a good idea to keep ATC in the loop. You would more than likely require some time to sort things out with the assumption that you would complete the required abnormal checklist. There are significant runway implications for most aircraft. For the B737NG as I recall a flaps up landing required a approach speed of Vref40+55, and plenty of runway. The reference required runway was around 1215 metres for 60,000Kg and 160Kg for every 5000Kg above 60K. So unless you were at an airport with long runways you may even have to consider diverting.

If you're asking if a FAR 121 airliner would land immediately following a slat/flap failure during ILS course capture the answer is absolutely not....and we would certainly notify the tower and roll CFR.

I'd notify Approach of your min speed as a courtesy so they can figure out spacing ahead of time rather than have them wonder why you are eating up the guy ahead of you then saying "unable" when they ask you to slow. They will pass it to tower.

keep everybody in the info loop. Runway Length is now an issue, different runway? divert? Some of the toolbags on another thread will snark at your "excessive radio chatter" but at the end of the day, you're in charge of your aircraft, not them. If in doubt , declare an emergency and you've just taken ownership of the airspace and runway. Be safe!

I'm discontinuing the approach, taking delay vectors, running the QRH and making sure I have enough runway...all while keeping the HMFIC onboard apprised of what is going on.

So, to answer the question...yes.

Why would I declare an emergency with ATC if in that environment?
Because I can not operate my aircraft in a normal fashion (much higher final approach speed) and therefore ATC needs to know that I will require special handling.
There are MANY variables here. Some may need extra time to run checklists. Some may need to make other decisions - like the different runways or airports that others here have mentioned.
For others it might not be such a big change other than a higher landing speed - which when taken into account with an appropriate runway might not be that much of a change at all.
It isn't black and white enough to have one answer fit all.

Although I wouldn't declare an emergency because wing flaps are not primary flight controls, I certainly would discontinue the approach. Notify ATC, short vector for QRH, landing data, etc.

That's generally a bad idea. While you might get an "implied" emergency situation, you are going to make it a lot tougher explaining to the FAA how you exceeded holding speed at 6000' and below or something else rather than just up front declaring the emergency and not having to explain around every regulation. That's what the whole "emergency authority" clause is for. Everyone is going to know about it already, so it'll be investigated by the company and regulatory authorities.

Many Pilots seem hesitant to Declare an emergency.

If the situation requires the Crew to go to the RED TABS or Non-Normal-Emergency Checklist, you will be better served just declaring an emergency.

This will do several things.
First an foremost it will alert ATC giving them a heads up and if/when you request something, it will be immediately be granted.
Second, abnormal Flap checklists can be busy and time consuming and should the crew deviate from an ATC or FAR procedure due to their preoccupation, they are covered.
Lastly, if on landing a tire is blown, or the aircraft strays from the runway or taxiway, or some other issue occurs not necessarily related to the Initial problem, you will regret (at the Long Green Table) that an Emergency was not previously declared.

Declare an emergency (Think Safety First)
Fly the Airplane
Handle the issue as you were trained
Land the airplane safely.

Later, Fill out an ASAP and you cannot be faulted.