MEL Question . to gear or not to gear

[Always Moving]

When do you put the gear down in a single engine NON PRECISION approach?
At the FAF? or
Whenever you can see and make the runway?

I know there is going to be controversy.....

[B2N2]

When do you put the gear down in a single engine NON PRECISION approach?

We need to get a couple of assumptions/criteria sorted:

• Light twin as in < 6000lbs
• Piston engines
• Approximately sea level conditions
• Circling approach vs straight in
• Pilot technique;
  "dive & drive" vs using calculated descent or VDP

There is no reason to treat a non- precision approach any different then a precision approach as far as rate of descent is concerned.
Where do you put the gear down in a single engine ILS approach?
The FAA used to recommend the dive & drive technique as in descending the the MDA as quickly as possible then leveling off and continuing to the runway.
They now recommend a calculated rate of descent or at least using the VDP.
The Visual Descent Point allows for a 3 degr. descent angle from MDA to the Touch Down Zone. This equals a rate of descent of 450-500fpm at our approach speeds. So from MDA you fly the VASI/PAPI.

A light twin can easily meet these (negative) performance criteria in approach configuration. In normal people "speak" : with gear down and approach flaps a light twin can (should) easily be able to descent at 450 fpm on one engine. Depending on the airplane you'll need approximately 65%-75% power setting. So if you fly the above mentioned descent profile, yes by all means put the gear down at or slightly prior to the FAF.

If you use the dive & drive technique you'll need to keep the gear up since most light twins are not able to maintain altitude (maintain MDA) with two drag factors; the flaps and the gear which means you'll have to sacrifice one, the gear.
Same applies for a circling approach, keep the gear up till you are in a position from which a normal descent to landing can be made eg abeam the numbers or on base.

So as far as single engine approaches are concerned:

• ILS - just prior to the intercept of the glideslope
• Non precision straight in - just prior to the FAF
• Non precision circling - on base
• Non precision with step down fix
  - just prior to the last IF

[Always Moving]

same same

B2N2 Thanks! I agree with everything you said
but.... If you do not have vertical guidance (and most light twins do not), or somebody to calculate for you the descend rate to arrive at the MP at your MDA there are chances or being too high, AND that is if you come out in front of the runway! hence the word NON PRECISION and if you come out too early then you would have to do a single engine maneuvering 2-3 turns depending of ability and increasing power and more rudder and it will end up a draged out approach, recipe for disaster.

I guess this will be one of those topics that different people have different opinions.

The way I see it
precision approach always at FAF
non precision 2 engines at FAF, 1 engine when you can land

[B2N2]

If you do not have vertical guidance (and most light twins do not), or somebody to calculate for you the descend rate

You don't need vertical guidance at least not in an instrument.
Some tricks that make this easy:

You don't want to reach MDA and the MAP at the same time, that's obvious.
The MAP is NOT the last point from which a normal descent to landing can be made. So what if we reach MDA one minute prior to reaching the MAP?
9 NM = 6 minutes @ 90 KTS = 5 minutes to descent
7.5 NM = 5 minutes = 4 minutes to descent
6 = 4-1=3
4.5 = 3-1=2
3 = 2 -1 =1 minute to descent to MDA

Youll need at least DME for this but it also works (less accurate) if ATC provides you with the distance on the approach clearance.

Let's assume that we are 6 NM from the MAP. That is 4 minutes at 90 kts.
Which means 3 minutes to descend. If we have 1800' to go that's 600fpm.
1500' remaining is 500 fpm.

To calculate the VDP the quick and dirty way: 3 x MDH
So if MDH is 500 AGL then VDP is 3 X 500 = 1500 = 1.5NM
If MDH is 750 the VDP is 2.2 NM
From the VDP it's a 3 degree descent to the runway.
So yes, it does depend a little on what equipment you have.

But I would use these tricks in a C152 with only VOR and no DME.
Full VOR approach, 4 minutes outbound, procedure turn; 3 minutes to descent on the inbound. If the winds are not too strong it works amazingly accurate.

[Martin Barnes]

In todays flight training senario where a low timer can be a frozen ATP,
Students ask these questions and will fly the aircraft in fixed configurations every time failing to realise that you fly the aircraft to suit the current weather conditions and aircraft weight.

For example if I loose an engine on a fully loaded PA31 or PA34 on take off
it will only just climb so I will baby it up to the altitude where I can level off.

I am not going to introduce any drag until I am ready to descend and then I will firstly descent to get a speed of at least blueline plus 10 kts before the gear is lowered. If im being vectored to an ILS against a strong headwind I will hold the gear until 2dme then slow down.

What Im saying is, If you are going to continue flying MEPL past the IR flight test, be aware that you cannot fly by the numbers to the same plan in all conditions.

[B2N2]

In todays flight training senario where a low timer can be a frozen ATP,
Students ask these questions and will fly the aircraft in fixed configurations every time failing to realise that you fly the aircraft to suit the current weather conditions and aircraft weight.

Agree...

Most common errors that I have seen with ME students is getting too high and too fast on SE approaches.
People also fail to realize that you lose 80% of your positive performance, not your negative performance.
You can fly a particular descent profile with both engines and you can fly the same descent profile with one engine.

[Mikehotel152]

IMHO the length of the MEP and Instrument Ratings here in the UK is not long enough to properly learn to fly the aircraft as well as learn to fly instrument approaches properly. The result of this lack of familiarity with the aircraft's performance is that the courses tend to teach rigid procedures and even where the pilot is given leeway he or she does not have the experience to make a good, reasoned decision.

Moreover, most light twins used for the IR are simply not up to the job. They can only just maintain level flight at the recommended SE approach speed! And that's with masses of rudder - try the DA42, it's tiring! Nevertheless, rightly or wrongly, we were told to put the gear down when base turn was complete and no later than FAF. I was partialled for not following this 'rule' on the basis that it was therefore an unstable approach.

[Tinstaafl]

If it's an assymetric runway approach then gear down at the FAF or GS intercept or equivalent place adjusted for distance & head/tailwind effects. If it's an assymetric circling approach then gear down when I commence descent to land after becoming visual. That could be on base, final, downwind ie wherever a normal descent profile intercepts my flight path. Flap also gets limited or no use until a landing descent is commenced. For light aircraft I prefer 'dive & drive' over 'constant descent' - I like the extra time to become visual, especially during circling approaches - but I've also needed to do lots of no-DME nor Radar supported non-precision approaches. Lots of them didn't have any ATS services on the ground either so Wx reporting was forecast only.

For all-engines approaches gear down at the FAF, GS intercept or equivalent and flap at least to approach setting.