This set of Aircraft Design Multiple Choice Questions & Answers (MCQs) focuses on “Landing Gear and Subsystems – Seaplanes”.
1. What is seaplane?
a) Plane which can land and takeoff from the water
b) Plane which can only land on water
c) Plane which can only took off from water
d) Seaplane is always same as any other plane in terms of landing and takeoff location
Explanation: Typical definition of a seaplane is as follows: plane which takes off from water and lands on water is known as a seaplane. Seaplanes are capable of landing and takeoff from water. Seaplanes are not necessarily same as other types of aircrafts.
2. If a seaplane needs to be designed then, which of the following could be considered as an application of the seaplane?
a) Search and rescue mission
b) Can be operated for every wave size in sea
c) Low value of wing loading
d) Ratio of weight to reference area is minimum among the other types of aircraft
Explanation: A typical seaplane can land and takeoff through water only. If we were given the task to design a seaplane then, one of the most applicable use of such plane would be for search and rescue. In fact, seaplanes are being used for such tasks. However, seaplanes cannot be used for every size of wave.
Explanation: A typical seaplane geometry is shown in the diagram. A seaplane is unique kind of plane which is capable of takeoff and land through water. F16 and Mig21 are fighter aircraft and are not seaplanes. Aerostats is different type of aircraft.
4. The hull of seaplane is based on the planning-hull concept.
Explanation: Hull sizing is one of the important factor in seaplane design. The seaplane hull and pontoon of float plane are based on the planning-hull concept. Typically, bottom is fairly flat. This allows the aircraft to skim on the water.
5. Which of the following is correct?
a) Typically, bottom of the seaplane is fairly flat
b) Lift is same as weight always
c) Drag polar will show thrust vs weight
d) Seaplanes cannot land on water
Explanation: Typically, bottom of seaplanes are made fairly flat so that seaplane can skim on the top of water even at high speeds. Lift is not always same as weight. Drag polar is schematic diagram illustrating relationship between drag coefficient and lift coefficient.
6. Most of the sea plane is designed with _________
a) v shaped bottom
b) h bottom
c) v shaped bottom only
d) flat bottom only
Explanation: Most of the seaplanes are designed with V shaped bottom. The V shaped bottom can be used to reduce the water impact Loads. However, few seaplanes were built with flat bottoms also. Hence, correct option will be v shaped bottom.
7. For higher landing speed, deadrise angle should be __________
d) independent of speed
Explanation: Deadrise is defined as the height of V in v shaped bottom. The angle is called deadrise angle. Deadrise angle should increase for higher landing speed. Deadrise angle is increased towards the nose of the plane. Deadrise is dependent on speed also.
8. If a seaplane has velocity at stall as V mph then, what will be the value of deadrise angle?
a) ɑdeadrise = 0.5*(v – 20) degree
b) ɑdeadrise = 0.5*(v / 20) degree
c) ɑdeadrise = 0.5*v degree
d) ɑdeadrise = 0.5*(v2 – 20) degree
Explanation: When we use V shaped bottom on seaplane, deadrise is then defined as the height of the V and angle is called deadrise angle. Typically, deadrise angle can be approximated as follows, ɑdeadrise = 0.5*(v – 20) degree where, v is stall speed in mph.
9. Let’s consider we want to design a seaplane which has the deadrise angle of 10° then, what should be the stall speed in in miles per hour?
Explanation: Given, ɑdeadrise = 10°
Now, stall speed can be given by,
V = 2 * ɑdeadrise + 20 = 2*10 + 20 = 40mph.
10. A seaplane has beam of 5 unit then, estimate the step size required for given seaplane.
a) 0.25 unit
b) 9 unit
c) 1.2 unit
d) 4.6 unit
Explanation: Approximate value of step size = 0.05*beam = 0.05*5 = 0.25 unit.
11. Typically, seaplanes can be categorized as ______________
a) floatplanes, flying boat, etc
b) floatplanes only
c) flying boat only
d) aerostats only
Explanation: Typically, seaplanes can be divided as follows: Floatplanes, flying boat etc. Aerostats are type of aircraft. Aerostats are driven based on buoyancy. They are lighter than air vehicle. Typical seaplanes are categorized as heavier than air vehicle.
12. None of the seaplanes can ever land on airfields.
Explanation: There are some seaplanes which are able to land on airfields. These are more broadly known as amphibious aircraft. They are designed in such way that they can land and takeoff through both water and land. Hence, given statement is not correct. Therefore, the answer will be ‘ false’.
13. Which of the following is an example of seaplane?
a) Curtiss NC
b) A321 neo
d) Cessna 172
Explanation: Curtiss NC is an example of seaplane. A321 neo is a commercial fixed wing aircraft that can only land or takeoff from the airfields. Cessna 172 is a prop aircraft that is not a seaplane.
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