Brian
Lv 4
Brian asked in Cars & TransportationAircraft · 10 years ago

# Positive Static & Dynamic Stability?

I do not really understand those in my Test Prep book, their explanations, even with the diagrams. It is a little confusing. I am a student pilot, so please give me some lee-way. Can you please explain this a little better? Thanks!

Relevance
• 10 years ago

Positive static stability means the aircraft will continue on the path it's on if it is not disturbed.

Positive dynamic stability means it will return to the original path after being disturbed.

Some aircraft like the C-172 have negative static stability around the yaw axis. If left alone they will go off course and fly in a large circle. The pilot makes constant corrections to stay on course. Other aircraft like a Beech Skipper have so much dynamic stability around the yaw axis that they dutch roll or waddle as they fly straight ahead. The pilot can damp the waddle out with constant input to the rudder or just waggle along. The designers of these two aircraft made a couscous choice for one kind of stability over the other.

• Erika
Lv 4
4 years ago

Dynamic Stability Definition

• FanMan
Lv 5
10 years ago

Static stability: Picture a marble in a bowl. Move it, and it rolls back to the bottom center. That's positive static stability (it is stable). Put the marble on a flat plate. It stays put wherever you put it, but it doesn't tend to go back to center; that's neutral static stability. Now put the marble on top of an upside down bowl; not only does it not stay put but it rolls faster and faster away from the center. That's negative static stability. Similarly, a statically stable airplane, if you pull its nose up and then let go of the controls, will tend to nose down and return to level flight, perhaps after a few oscillations.

Now picture the marble in the bowl again. If move the ball to center, it rolls back and forth a few times, less and less each time, until it stays put in the middle (like the airplane above). But supposing the ball kept rolling back and forth, rolling higher and higher each time until it flew out of the bowl? It's not possible in the real world with a ball and a bowl, but if it was, that'd be positive static stability and negative _dynamic_ stability. Similarly, a statically stable airplane might climb, then dive a bit more than the climb, then climb a bit more than the first time, then dive even steeper, etc... that, again, is positive static stability and negative dynamic stability.

• Anonymous
5 years ago

For the best answers, search on this site https://shorturl.im/avZBB

Tai Chi Chuan and balance in elderly people Scientific background About 30% of people over 65 years old sustain a fall, and this often leads to hip fracture and severe disability. Tai Chi (shadow boxing) is widely practised in China and has been shown to cause both physical and spiritual benefits, especially in old people. It has been noted that regular practitioners of Tai Chi seldom suffer falls and hip fractures in old age, probably because they have good muscular coordination and a calm personality. Aim of investigation To see if the mental and physical stability and co-ordination of people regularly practising Tai Chi is better than that of age- and fitness-matched controls who do not practice Tai Chi. Method Volunteers aged 65-80 years will be recruited who have attended sessions lasting 30 minutes at least twice weekly for 2 years at a well-established Tai Chi school on the outskirts of Birmingham. This is led by a master who has a thorough understanding of the philosophy of Tai Chi. Control subjects, matched for age, gender, fitness (assessed by pulse rate during a standard step test) and duration of regular attendance will be recruited from a neighbouring keep-fit class led by a qualified physiotherapist with no knowledge of Tai Chi. Measurements of static postural stability, dynamic balance and muscular co-ordination will be made in the Birmingham hospital rehabilitation unit by staff who are blind to the treatment group of the subjects being tested. Mental state of participants (especially confidence and anxiety) will be assessed by the Minnesota questionnaire: the completed forms will be sent for scoring to the hospital Department of Clinical Psychology. All the forms (identified only by a code number) will be scored independently by two clinical psychologists who are blind to the treatment group. Analysis and interpretation The 5 major endpoints (postural stability, dynamic balance, muscular co-ordination, confidence and anxiety) will be compared within each pair of Tai Chi and control, and the results analysed by a sequential design. For each end-point, in each test-control pair, the result will be scored positive if the test individual scores better, negative if the control scores better, and the result is discarded if the two are exactly equal. With this design to reach a significant result (P<0.05) will require a minimum of 7 and a maximum of 48 pairs to reach the top boundary (Tai Chi better) the middle boundary (no significant difference) or the lower boundary (control better). The hypothesis will be supported if at least 3 of the 5 end-points reach the upper boundary.

• 5 years ago