B737 nosewheel landing?

[Gin Slinger]

Let's say we're light, using flaps 40 due to runway length considerations. How easy is for the nosewheel to contact the ground before the maingear?

If I retard the thrust leavers so they come to idle at touchdown, as Mr Boeing says, I only flare marginally or I balloon up in the air, but conversely it's in the back of my mind is that the nosewheel is perilously close to the ground.

[blackmail]

hello gin slinger,

there are only 3 ways to make a good landing, the problem is that nobody knows them.
that aside, if you use standard landing procedure, eg, first of all a good landing results from a stabilised approach: attitude, thrust,configuration & speed correct, then when you hear the call out "20"ft(radar altimeter or pilot non flying, pnf), thrustlevers idle, arrest the nose drop with the yoke, look far away to the rwy end & wait for ground contact with the mean gear, then fly(not drop) the nosewheel to the rwy, check speedbrakes up, apply reverse & brakes (auto or manual), keeping the aeroplane on the centerline with the rudder.
using these techniques either with flap30 or flap40 will minimise risking nosewheel contact first.

[Gin Slinger]

Thanks for that - I understand everything you say, but does anyone have any figures for nosewheel clearance during 'typical' light weight F40 landing?

[Rivet gun]

It seems to me that if you have the correct Vref for the weight, the pitch attitude on touch down should be the same regardless of weight (for a given flap setting).

Wheelbarrows happen due to landing too fast (I think)

[blackmail]

hello gin slinger,

the nosewheel clearance on touch down is function of the body pitch attitude & the body roll angle. the boeing flight training manual, section "manual flight", where for different models 737-2/3/4/5, some charts illustrate the combination of body pitch angles on the vertical axis & body roll angles on the horizontal axis at which nose gear/nacelle/flap track fairing/aft fuselage will contact the runway. a note says: these charts assume struts compressed, flaps40 & are valid for all sink rates. approx. 1 second after touchdown. for flaps 15 & 30, greater clearances exist at some roll angles.

so let us do some math's:according to the graphs, at 0° body angle & 0° roll angle the nose gear touches the rwy. for a b737-300, distance between main gear & nose gear is 12.45m or 40.8464ft.
if we do everything right we come in at 0° pitch attitude/0° roll, flaps40, vref+5(wc<10kts) on a 3°/5% glidepath, in the flare we raise the nose to eg 3°/5% & touch, then simple trigonometric calculations gives nose gear clearance = 40.8464ftx0.05= 2 feet.

0.6°=1%

if we raise the nose 5°/8.3%, then the nose gear clear.= 40.8464ftx0.083= 3.3902512ft.

i think normal flare techniques to be within these values( 3 a 5°).

if we raise the nose to 11° tail strike occurs & nose gear clearance becomes irrelevant.
i let you do all the other intermediate flare combinations.

[PAXboy]

(non-pilot speaking and I appreciate that there wil be many variables in this question, such as speed and so on) If the nose gear touches first, is this simply uncomfortable? Is it bad news? or is it really bad news??

[Gin Slinger]

Firstly, thank you blackmail. Your sums are of course reassuring and entirely logical.

Paxboy: the maingear are seriously beafy and designed to absorb the forces associated with landing, whereas the nosegear is designed only to support the front of the aircraft and steer it on the ground. Land on the nosewheel, it will probably collapse, or at least cause structural damage.

The technique is to raise (flare) the nose up wards just before touchdown to reduce the rate of descent, 'cushioning' the landing. This will also ensure the maingear lands first and takes all the shock load, then the nosewheel is gently lowered ('flown') onto the runway. Nosewheel first landings are more of a problem with light aircraft, whereas jets fly down the approach with a positive pitch angle (i.e. nose pointing up wards), a light aircraft flies down the approach nose down, and requires a good tug on the control column momentarily before landing to prevent the nosewheel hitting the deck first.

[Final 3 Greens]

PAXboy

In 15 hours of training on a "big iron" sim, I only landed on the nosewheel once. (Fortunately, i've never done it in a light aircraft in several hundred landings.)

But that caused the screen to go blank and the computer to reset the scenario.

I think that this means it is really bad, bearing in mind that the sim is not a video games, with lots of freaky graphics - blank screen definitely means tea with the chief pilot - in my case, as an amateur, it was restricted to buying beer for the instructor ;)

Even as a rank amateur, I can understand Gin Slingers concern (and I did it at gross landing weight, which makes it even more inexcusable.)

[FlightDetent]

Half of our fleet is -400 and for reasons that be we use flaps 40. I have landed a plane with nothing but 3 tons of fuel onboard, also did the same 200kgs below the increased maximum LW. I think there is no difference in pitch on approach (agree with the above) and it is still positive albeit marginally, 0.0+ to 1,5 deg, wind dependant.

Thus even with no flare the mains hit the ground first.