DA40 Max Landing Weight

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ethos

DA40 Max Landing Weight

Post by ethos »

I started renting a DA40 with MGW 2664 and MLW 2535.

Just recently got my PPL so be gentle with me.

The manual states in section 4B.7 a higher approach speed for above MLW and that the MLW was for " highest mass for landing conditions at the maximum descent velocity" with a warning that damage can occur for a hard landing above MWL.

Since the landing with high mass is under the abnormal procedures list, i get the impression it is more for a forced landing prior to burning the weight off rather than OK-ing landing at higher-than-MLW with the listed approach speed.

This the right track?
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BlackMammoth
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Re: DA40 Max Landing Weight

Post by BlackMammoth »

The FAA requires specific tests to determine max landing weight. We upped our certified gross weight by replacing the landing gear on our DA40.

Note: Forgetting the FARs and the FAA. My comments are directed towards engineering structure limits.

If you can execute something approximating a "Normal" landing you are not going to have a problem structurally. The rules are based on a worst case scenario landing.

My belief is thus: You take off on what should be a "normal" flight. Should you be forced to return early this becomes a non-typical situation.

Save yourself and your passengers before you worry about FAAisms. However, don't flaunt these rules as they are based on keeping you safe in almost any controlled landing.
ethos

Re: DA40 Max Landing Weight

Post by ethos »

Thanks.

I'm planning on starting with 32 gal to be within both limits for my trip but wanted to make sure i was in line with the common understanding of the manual.
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Lance Murray
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Re: DA40 Max Landing Weight

Post by Lance Murray »

"Since the landing with high mass is under the abnormal procedures list, i get the impression it is more for a forced landing prior to burning the weight off rather than OK-ing landing at higher-than-MLW with the listed approach speed."

The most conservative answer to your question is:

If you take off above your maximum landing weight and have a need to land above your maximum landing weight you should declare an emergency (if uncontrolled declare it to yourself) and land. After landing have your mechanic perform an overweight landing inspection IAW the Diamond Aircraft Maintenance Manual. Declaring an emergency relieves you from any regulation, procedure or limitation as necessary to deal with the situation. The laws of gravity and physics still apply however.

No one will EVER question you and there is ZERO jeopardy if you do the above unless your overweight landing is due to your own lack of pre-flight planning. Land normally carrying the recommended speed and you will be fine.
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Re: DA40 Max Landing Weight

Post by rwtucker »

You are getting sterling advice on the regulatory and practical issues associated to your question. Speaking strictly to the issue of minimizing or avoiding damage in a landing, the most sensitive variable is velocity per [KE = 1/2mv^2]. Therefore landing at absolute minimum v with a bump may produce less stress on the airframe than a somewhat smoother landing at 10 kts above v. Of course, you want to pay attention to both variables, and they get complicated in real landing vectors, but we sometimes forget the power of v^2.
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Re: DA40 Max Landing Weight

Post by Guest »

I think it would only be the vertical component of V that you are worried about, as it is hard to imaging braking inducing loads on the landing gear that they cannot handle.

I remember a 747 pilot on a flight out of Moscow for NY talking about a passenger with an acute MI. He had to put it down in Helsinki with full fuel. Basically they looked at the wind conditions, figured it was smooth enough to put it down gently, and went for it rather than dump thousands of gallons of Jet A into the Baltic.
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Re: DA40 Max Landing Weight

Post by Boatguy »

Guest wrote: Sat Feb 13, 2021 4:17 pm I think it would only be the vertical component of V that you are worried about, as it is hard to imaging braking inducing loads on the landing gear that they cannot handle.

I remember a 747 pilot on a flight out of Moscow for NY talking about a passenger with an acute MI. He had to put it down in Helsinki with full fuel. Basically they looked at the wind conditions, figured it was smooth enough to put it down gently, and went for it rather than dump thousands of gallons of Jet A into the Baltic.
That's challenging to believe. It's at least a one hour flight from Moscow to Helsinki and burns a lot of fuel on climb out at MGTW. When I worked for an airline which flew DC-10's, pilots could not land over the plane's max gross landing weight of 525,000. Period.

What airline's operations center told a pilot to land over MGLW?
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Re: DA40 Max Landing Weight

Post by Lance Murray »

For a frame of reference. The 747-8 MGTOW IS 967,000# MLW is 763,000#. Burn the first hour is probably around 25,000#. You would have to jettison or burn over 200,000# of fuel. Not too hard to believe. You would have to fly 4-5 hours to get below landing weight or the fuel can be jettisoned in a relatively short amount of time.

That’s a hard call to make a high risk landing to help a single medical emergency. But....maybe the Captain thought it best. That’s his call and in an emergency he may deviate from FARs and limitations to the extent necessary. Remember that the PIC is always in command no matter what. He/she may just need to use the magic word.
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Re: DA40 Max Landing Weight

Post by Lance Murray »

“What airline's operations center told a pilot to land over MGLW?“

None. The decision is the Captain’s alone. He is the final authority and solely responsible.
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Re: DA40 Max Landing Weight

Post by Rich »

Before the MTOW/MLW change the numbers were:
MTOW: 2535 lb.
Max zero Fuel weight (irrelevant, though implicit and not reasonably attainable): 2535 lb.
MLW 2407 lb. (21.3 gal fuel burnoff required.)

After:
MTOW: 2646 lb.
Max zero Fuel weight now explicitly defined: 2535 lb.
MLW 2535 lb. (18.3 gal fuel burnoff required.)

I've flown other light aircraft where there was a difference. One example that comes to mind was a Comanche 260 with a 200 lb. difference. That had a knob on the panel you could pull to dump fuel in the air.

The guidance in the POH for above-spec landing weight amounts to "touch down gently" :D
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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