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Power off landings - glide slowly, or glide fast?

Timothy wrote:

TDODAR is grist to the mill of professional flying and is gaining traction in GA and private flying.

Around here they call it FORDEC. I have also heard of DODAR (when training with Flight Safety in the UK). But TDODAR with a leading “T” is a first for me.

EDDS - Stuttgart

Pilot_DAR wrote:

If you arrive to the top of the flare with no excess airspeed – flying slower than “best glide speed” or just a little faster than stall speed for that configuration, if you pull for some upward acceleration to arrest the descent rate, the plane will stall, and just keep going down with a thump.

This is where I think you’re going wrong. You associate “best glide speed” with being just a little faster than stall speed. But in any aircraft I’ve flown, they are a long way apart, and a normal, power off, approach speed would fall in between them.

The aircraft that I fly these days has a best glide speed of 105mph. Flapless stall speed is about 55mph. A normal approach is made with 1/2 flaps at 80mph (so half way between the two) and slowing to 75mph “over the hedge”. The last 100ft are flow with engine at idle and will only be used again in the event of a go-around. So the last 100ft are the same as would be in the event of an engine failure.

The suggest that flying slower than best glide (105mph) is leaving insufficient energy for the flare is incorrect; in fact flying slower than best glide is normal (and recommended POH) procedure. If I was to start my flare at best glide speed, I’d need an extremely long field, and where my touch down point would be a matter of luck rather than judgement.

I can’t see why anyone would suggest that approaching at the approach speed recommended in the POH, would leave the aircraft dangerously uncontrollable. Clearly that’s not the case.

EIWT Weston, Ireland

Timothy wrote:

TDODAR is grist to the mill of professional flying and is gaining traction in GA and private flying. It is used in most airlines, including BA. I teach it on my seminars and when training. I am surprised that it is considered obscure.

The concept (but not the acronym) is included in the IR TK (don’t know about the CB IR). It took me ages to memorise the various steps.

ESKC (Uppsala/Sundbro), Sweden

The T in TDODAR is only to ascertain that you have Time for DODAR. If you don’t (for example, an engine fire warning at Vr -10) then you just have to react without further diagnosis.

EGKB Biggin Hill

Timothy wrote:

The T in TDODAR is only to ascertain that you have Time for DODAR. If you don’t (for example, an engine fire warning at Vr -10) then you just have to react without further diagnosis.

I prefer the USAF mantra quoted by Nate @Buster1 in his excellent book.

Sir/Ma’am, I will maintain aircraft control, analyze the situation, take proper action, and land as soon as conditions permit.

EGTK Oxford

dublinpilot wrote:

You associate “best glide speed” with being just a little faster than stall speed. But in any aircraft I’ve flown, they are a long way apart, and a normal, power off, approach speed would fall in between them

Fair enough, if the “best glide speed” is faster, then it’s probably just where you want to be for a power off approach, carrying some reserve energy for the flare. A number of types I have flown have a more slow “best glide speed”, optimized for greatest distance covered for altitude lost (which is the design requirement – so fair be that). But for some aircraft, this speed will leave the pilot little reserve to flare, particularly if poorly executed. Doable, but demands precision.

There may be quite a difference between best glide speed, and the stall speed. The flaps extended stall speed will be slower yet. It’s worthy of note that a power off flare with full flaps extended may result in a more rapid slowing. Thus, if the flare is too high, and you were power off, full flaps, you’ll be challenged to recover the flare at the runway. If you have carried extra speed, you have a little reserve to play with.

I observe that power off landings (from the turn to final) are not often practiced by most pilots. Those few flights a month, usually somewhere, with someone, do not lend themselves to PFA’s. My goal is to remind pilots that it’s worth being practiced in actual PFA’s to an actual touchdown. With practice, they can be flown at slower speeds. Before that skill is perfected, a little extra speed is a little extra stored energy, money in the bank so to speak. If you don’t need it, you can slip it off in the latter stages of the approach. Many types I have flown can be easily slipped well into the flare if need be.

To drop a name, it was well known test pilot John Farley who told me that if it quits, point the plane where you think you can crash best, then just don’t crash when you get there. This is a pilot who tells me of gliding a Hawker Harrier to a power off landing. I wonder if there is even a best glide speed published for the Harrier – when “eject” is an option! If the space shuttle can be neatly glided to a precise landing, anything can! It’s just a matter of working out the speeds, and sight picture.

Home runway, in central Ontario, Canada, Canada

land as soon as conditions permit.

So, the action is included in the mnenomic? Before you start the diagnosis, you decide that you are going to land as soon as possible?

You will know of the BA 747 which had a engine failure on departure at LA and then continued to the UK, because the crew went through TDODAR and calculated that they could continue with the flight.

Or, better example, you diagnose something that can be completely fixed (let’s say throttle friction was loose, or you carry a spare that can be fitted in flight) and so there is nothing wrong with the aircraft.

I am surprised that the USAF and you think that that should result in a landing as soon as conditions permit.

EGKB Biggin Hill

You will know of the BA 747 which had a engine failure on departure at LA and then continued to the UK, because the crew went through TDODAR and calculated that they could continue with the flight.

That was a “interesting” piece of decisionmaking, given that they could not have known what collateral damage was done by the engine shredding itself, to other aircraft systems. IMHO they continued to the UK because

  • it was not prohibited in their AOC manual
  • head office didn’t want a 747 full of angry people stuck in the USA (a career limiting move for a pilot if there are other options)
  • much of the immediately ongoing flight was over US mainland and with lots of landing options

They were forced to land short due to low fuel, at Manchester IIRC, so it was a “bit tight”… but rescuing passengers out of Manchester costs a lot less.

But even so, having 4 engines and 2 pilots is not the usual GA scenario, surely?

Administrator
Shoreham EGKA, United Kingdom

(t)DODAR is a development of the Boyd Cycle (often called the OODA Loop). John Boyd was a USAF fighter pilot during the Korean War who became an expert in military strategy, subsequently prescribing the decision making cycle. OODA represented Observe, Orientate, Decide & Act. The key bit was ‘looping back’ to Observe. There are now many other flavours of the same principle out there – DODAR, PIOSEE etc. Interestingly, t was added to DODAR some years back as some operators found that Biggles tended to happily kick-off the decision making cycle at V1 which, as Timothy has already stated, was not an astoundingly good course of action.

Fly safely
Various UK. Operate throughout Europe and Middle East, United Kingdom

Timothy wrote:

I am surprised that the USAF and you think that that should result in a landing as soon as conditions permit.

Well I guess different things work for different people. If after taking proper action the problem is resolved then I would of course not land. I do though think for private pilots that if a problem cannot be fully resolved or determined to be something as simple as a friction nut then a presumption to get the plane on the ground is a good one to have. I also like the affirmation to maintain control which TDODAR doesn’t have.

EGTK Oxford
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