I’m used to the TB20 flap limiting speeds in my aircraft of 129 and 103 knots for first and second stage respectively.
First stage flap and gear down are deployed at the FAF on an instrument approach, flown at 110 knots.
On becoming visual, the second stage can be deployed which requires a prior loss of about 10 knots.
Alternatively, landing with one stage is quite feasible and advisable in conditions with low minima when there is little time to reconfigure or in very strong winds.
I’ve flown a TB10 recently and was surprised to read in the checklist and POH that the flap limiting speed is 95 knots.
Unlike our TB20, the flaps are deployed by continuously operating the flap motor rather than selecting a position.
I can’t find a distinction between first and second stage limiting speeds which surprises me.
I would think that flying an approach clean at 110 knots would still be appropriate, but it means a much larger transition prior to deploying full flap and makes it more likely to land flapless.
Can anyone with more familiarity of the TB10 comment?
As per our offline discussion, but in case this helps anyone else my understanding is as follows.
For the TB20 the ability to use first stage of flap at 129kts as opposed to 103 only arrived with serial numbers in the late 800’s, prior to this use of any flap was restricted to 103kts. Earlier versions of the TB20 (not sure about 10 yet) CAN have the flap limit speed changed as long as MOD 27-50 is implemented. I dug out this modification and it is, low and behold, a flap pre-selector to replace the continuous run/infinitely variable selector.
Logic I presume is that with a pre-selector the flaps will only deploy to the specified position, whereas without pre-selector it would be possible for the pilot to set a position anywhere and potentially take the flaps to where a structural problem may arise.
MOD 27-50 is applicable for the TB10 but I haven’t yet found any supporting documentation that says what the flap limit for first stage would change to, if it all. Either way, I think the 95kt restriction applies.
The IFR Supplement for the TB10 is suggesting: Clean, 2500 RPM / 14.8 Mp to give 92kts IAS with a 3 degree glide path. I suspect this will yield more than 92kts personally and having the take off flap deployed doesn’t massively add to the drag hence the issue of staying inside the 95kt limit if one attempts that configuration.
It’s not ideal – the flap limiting speed is too low really.
I fly instrument approaches clean at 100 knots and will generally add the first stage of flap on becoming visual, reducing power to bleed speed while holding the glideslope. Any runway with an instrument approach is long enough that one doesn’t need full flap so I don’t tend to use it – although I sometimes have. Depends on things like where the runway exit is and whether there’s much of a crosswind.
I could fly instrument approaches at 90 knots with one stage of flap, but then not busting 95 knots becomes one more thing to think about. I also find it easier to hold the needles when going that bit faster – control response is better and it rides the bumps better.
All visual approaches I use full flap unless specifically practicing without it, but I don’t tend to add it until on fairly short final – there isn’t much point dragging it in slowly on the back of the drag curve with more power than necessary.
Thanks both, especially @Whiskey_Bravo for sharing some very thorough research.
I agree with Graham’s view that holding the needles is a bit easier with the slightly extra speed. It also reduces the time taken to fly the approach which helps ATC manage traffic flow, and helps offset stronger headwinds
Looks like we have a general consensus for an instrument approach speed of 100 knots clean with one stage deployed after going visual and optionally two on short final.
