Disturbance Theory Research Articles

Long-term demography and stem productivity of Everglades mangrove forests (Florida, USA): Resistance to hurricane disturbance

Mangrove wetlands along coastal regions in neotropical northern latitudes are exposed to frequent hurricanes and therefore depend on resistant and resilient attributes to persist after these extreme events. However, few long-term studies have documented mangrove forest dynamics following hurricane disturbance to determine how species-specific phenotypic plasticity, species range shifts, and environmental stress interact to determine recovery trajectories. We present here a comprehensive analysis of Hurricane Wilma’s (hereafter, “Wilma”) impact (category 3, October 2005) on mangrove forest demography and aboveground net productivity in the Everglades, Florida (USA). We determined spatiotemporal patterns over a 15-year period (5 pre- and 10 post-Wilma) in three impacted sites on a productivity gradient along the Shark River Estuary. Hurricane resistance was evident in the low cumulative tree mortality and long-term recovery from defoliation (∼10 years). Aboveground standing carbon stocks were not significantly reduced, as mortality ranged only from 3 to 10%. A negative linear relationship between Leaf Net Primary Productivity (NPPL) and foliar residence time along the estuary shows that an increase in foliar production results in shorter residence time, which is defined by the interannual variation in NPPL rates and recovery periods across sites. We propose this relationship as a proxy of canopy recovery in latitudinal comparative studies across mangrove ecotypes and coastal settings. This work advances ecological disturbance theory and ecological modeling of mangrove forests; specifically, we provide quantitative relationships among structural properties and dynamic processes to validate agent-based demographic and biogeochemical models to forecast the impact of natural and human disturbances on mangrove wetlands under climate change.

Bandwidth Based Stability Analysis of Active Disturbance Rejection Control for Nonlinear Uncertain Systems

This paper focuses on the stability analysis of the active disturbance rejection control (ADRC) for a class of uncertain systems. To overcome the difficulty of defining a reasonable Lyapunov function and setting limitations of system parameters, the converse Lyapunov theorem and the disturbance theory are employed. This paper proves that the estimation error of the extended state observer (ESO) and the tracking error of the closed-loop system using ADRC are uniformly ultimately bounded and monotonously diminishing with the increase of their respective bandwidth, so that the stability of the ADRC system could be performed. In order to further illustrate the relationship between the stability range and bandwidths, it analyzes quantitatively the performance of ESO and ADRC based on the root locus and the step response. Finally, an example based on a typical control system is carried out, and simulation results verify the theoretical analysis proved in this paper.

Habitat structure and host plant specialization drive taxonomic andfunctional composition of Heteroptera in postfire successional habitats

Changes in habitat structure are the main driving forces for responses of animal assemblages to fire. According to the disturbance theory, generalist species are expected to outperform specialists in variable environments. Thus, we hypothesized that omnivorous and polyphagous species will become more abundant in unstable postfire successional vegetation, whereas monophagous (specialists), due to their strong dependence on host plants, are expected to respond according to the responses of plant hosts. We compared the responses of true bug (Heteroptera) assemblages in stable (unburnt) versus unstable (postfire successional) environments as this group shows a high diversity of feeding strategies. Redundancy analysis fitted our hypothesis as omnivorous and polyphagous bugs responded positively to fire whereas oligophagous bugs did not. Thus, the most generalized bugs in terms of diet were found in disturbed (burnt) habitats whereas specialized bugs were found in undisturbed (unburnt) habitats. Moreover, the most specialized bugs (monophagous species) responded to fire in accordance to the responses of their specific host plants. Although based on small bipartite networks, the lower modularity in burnt sites corresponded to a scenario of lower segregation of plant resources and fits the higher presence of generalist bugs in these sites. Our results suggest that plant?bug trophic interactions shape the response of Heteroptera to fire, and this response seems to be mediated by the degree of feeding specialization.

An Exploratory Study of the Impact of Top Leadership on Effectiveness of Privatization of Hospitals Through Mergers and Acquisitions in Kenya

This paper examines the privatization of hospitals through mergers and acquisitions (M&A) using Kenya as the country of focus. It shows that M&A activities are increasing in Africa and there is a history of privatization of state-owned enterprises (SOEs) / parastatals in Africa and Kenya in particular, which started in the 1990s. With the changing dynamics, increasing pressure to achieve universal health and looking at the history of mergers and acquisitions there is no doubt that this is going to become an important phenomenon in Kenya in the near future.Privatization of hospitals, including public and not-for-profit (NFP), has been popular since 1980s in North America (U.S., Canada) and Europe (Germany, England). Privatization and M&A activities of hospitals in other countries such as India, China, Saudi Arabia, Africa and Kenya have also increased. The reasons for these trends are industrialization of developing countries, changing lifestyles, aging populations, longer life expectancy, technological advancement, growth of the middle class, increase of non-communicable diseases (NCDs) and inefficiency of public health systems. With the changing dynamics, it would appear there is a need for African countries to expand their private sectors, and privatization of healthcare is an attractive area for private equity firms and private hospital chains. Due to growth of the economy and the middle class, higher demand for healthcare services and particularly expansion of NHIF (National Hospital Insurance Fund) coverage, privatization of hospitals makes economic sense in Kenya.Knowledge of M&A among top leadership is crucial in determining its success or failure. Therefore, the literature review focused on property right, transaction cost, and institutional theory. Relevant M&A theories such as process, synergy, efficiency and disturbance theory were also reviewed.The research philosophy, methodology and design of this study was based on exploratory, post-positivism, deduction and utilized mixed methods (qualitative and quantitative) with focus on verifying the hypothesis. The population of this research included Level 4, 5 and 6 hospitals in Kenya, totaling 268 hospitals with at least 50 beds; the sample size was 158 hospitals. Proportionate stratified random sampling methodology was used to determine the sample size of each hospital level (Level 4, 137 hospitals; Level 5, 14 hospitals; and Level 6, 7 hospitals).The hypothesis that there is no relationship between top leadership (X) and the effectiveness of privatization of hospitals (Y) through M&A was tested and there was a strong and positive relationship between the dependent and independent variables (r=0.821), and the regression model was found to be reliable. The null hypothesis was rejected because of the results of the T-test (β1=0.925, t=9.757, p<0.005).It is recommended that similar studies be conducted in East and South Africa to enable researchers to perform comparative analyses in order to improve the body of knowledge.

Hypersonic dynamic stability of wave riders

PurposeThe purpose of this paper is to obtain close form expressions for the dynamic stability of conical wave riders with flat surfaces which could be equipped with lifting surfaces on its plain flat surface. Numerical simulation would require very large meshes to resolve flows at subscale level and the experimental evaluations would be equally difficult, requiring expensive measurement facilities with challenging procedures to secure such vehicles in confined test sections to obtain satisfactory wind on and wind off oscillations.Design/methodology/approachThe design method uses appropriate pressure fields using small disturbance theory, which, in turn, is perturbed using the unsteady shock expansion theory to recover suitable expressions for the dynamic stability behaviour.FindingsIt was observed that the dynamic stability of the standard half-cone-type wave riders with flat upper surfaces deteriorates with the axis position measured from the pointed apex reaching a minimum at around x/co = 0.666. The half-cone wave rider with flat upper surfaces is dynamically less stable than a pure cone.Research limitations/implicationsThe method is typically less accurate when the similarity parameter M∞θ ≤ 1 = 1 or if the angle of attack is not small.Practical implicationsWith renewed interest in hypersonic, future hypersonically would be designed as fast lifting bodies whose shapes would be close to the configurations of hypersonic wave riders, especially if they are designed to operate at upper atmosphere altitudes.Originality/valueThe analytic approach outlined in this paper for the evaluation of dynamic and static stability derivatives is original, drawing from the strengths of the small disturbance theory and shock expansion techniques. The method is particularly important, as there are no reported theoretical, numerical or experimental results in the literature.

Fire disturbance disrupts an acacia ant–plant mutualism in favor of a subordinate ant species

Although disturbance theory has been recognized as a useful framework in examining the stability of ant-plant mutualisms, very few studies have examined the effects of fire disturbance on these mutualisms. In myrmecophyte-dominated savannas, fire and herbivory are key drivers that could influence ant-plant mutualisms by causing complete colony mortality and/or decreasing colony size, which potentially could alter dominance hierarchies if subordinate species are more fire resilient. We used a large-scale, replicated fire experiment to examine long-term effects of fire on acacia-ant community composition. To determine if fire shifted ant occupancy from a competitive dominant to a subordinate ant species, we surveyed the acacia-ant community in 6-7 yr old burn sites and examined how the spatial scale of these burns influenced ant community responses. We then used two short-term fire experiments to explore possible mechanisms for the shifts in community patterns observed. Because survival of ant colonies is largely dependent on their ability to detect and escape an approaching fire, we first tested the evacuation response of all four ant species when exposed to smoke (fire signal). Then to better understand how fire and its interaction with large mammal herbivory affect the density of ants per tree, we quantified ant worker density in small prescribed burns within herbivore exclusion plots. We found clear evidence suggesting that fire disturbance favored the subordinate ant Crematogaster nigriceps more than the dominant and strong mutualist ant C.mimosae, whereby C.nigriceps (1) was the only species to occupy a greater proportion of trees in 6-7yr old burn sites compared to unburned sites, (2) had higher burn/unburn tree ratios with increasing burn size, and (3) evacuated significantly faster than C.mimosae in the presence of smoke. Fire and herbivory had opposite effects on ant density per meter of branch for both C.nigriceps and C.mimosae, with fire decreasing ant densities per meter of branch and the presence of large herbivores increasing ant density. Taken together, these experiments suggest that major ecosystem disturbances like fire can disrupt mutualistic associations and maintain diversity in partner quality and identity despite a clear dominance hierarchy.

Energy-loss Analysis of Thermal Power Unit Based on Multifactor Disturbance Theory

A new energy-loss analysis based on multifactor disturbance theory was studied in this paper. Due to the strong coupling characteristic of steam turbine system, the disturbance factors were decoupled and categorized. The main steam pressure, main steam temperature, reheat steam temperature and exhaust steam pressure were categorized as the large independent disturbance factors, while the terminal temperature differences (TTDs) of the regenerative heaters were categorized as small independent disturbance factors. The single-factor calculation method for energy-loss of heater TTDs neglected the interaction between each heater, thus all heater should be considered as a whole system when calculating the energy-loss of TTDs changes. The energy-loss of large independent disturbance was calculated based on global variable condition calculation method. Through calculating the energy-loss caused by the classified disturbance factors, the relative errors between the theoretical value and operation value were -3.00% for100%THA (turbine heat acceptance), -9.75 for 75%THA and 16.47% for 50%THA. The relative errors meet the requirements of the onsite guidance.

Applied ecology in Canada’s boreal: a holistic view of the mitigation hierarchy and resilience theory

Canada’s boreal biome is a mosaic of forests and peatlands. These ecosystems have developed dynamically, periodically affected by disturbance events of significant spatial extent and variable severity, reducing ecosystem biomass. The same ecosystem types typically regenerate from biological legacies. However, concern is growing about the impact of these different anthropogenic disturbances, particularly compound disturbances including climate change, which open the door to shifts to alternate stable states. One strategy promoted to regulate anthropogenic disturbance is the “mitigation hierarchy” for development projects, where impacts on ecosystems are avoided, mitigated, restored, or compensated. This practical approach is not yet integrated into disturbance and resilience theory. Here, I develop an integrated view of the mitigation hierarchy, as well as resilience and disturbance theory, in a boreal context using ecosystem services to measure ecosystem state in a two-step process that first models loss of ecosystem function and then integrates the mitigation hierarchy and resilience theory. The application of this model is discussed in the context of restoration studies after different types of catastrophic anthropogenic disturbance. These studies, some of which are published in this special issue, highlight the important role of bryophytes and understory plants in setting restoration targets and developing criteria and indicators of success.

Poplar plantations along regulated rivers may resemble riparian forests after abandonment: a comparison of passive restoration approaches

Abandoning hybrid poplar plantations may be an alternative strategy for enlarging natural riparian corridors along regulated rivers where forest regeneration no longer takes place. Despite the generally high local diversity of plants in poplar plantations, their capacity to converge towards riparian forests following abandonment remains largely untested and uncertain, because maintenance‐related disturbance of plantations favors ruderal, not strictly riparian specialists. We assessed the spontaneous recolonization of vegetation in abandoned hybrid poplar plantations following two management strategies: harvesting or simple abandonment of standing trees. The floristic composition in four chronosequences of 10 active (1–15 years), 17 harvested (1–15 years), and 10 abandoned (8–20 years) hybrid poplar plantations, as well as 10 riparian sites established at gravel bars that appeared following the cessation of in‐channel gravel mining (8–25 years) along the highly regulated Garonne River (SW France) was assessed in the framework of ecological disturbance theory. Both harvested and abandoned sites still resembled active plantations more than riparian forests. When poplar resprouting was low after harvesting, sites were dominated by light‐demanding, nitrophilous herbs, sub‐shrubs, and vines showing both competitive and ruderal traits, and vegetation composition remained stable over time. Abandoned and harvested sites with high poplar resprouting developed forest communities in which competitive species that tolerate and generate shade dominated, and tree species recruitment was higher. Riparian sites hosted the highest number of indicator species, mainly wetland and exotic. Simple passive restoration strategies like abandonment of plantations can help create valuable ecosystems, although ones that diverge from riparian forests colonizing new fluvial landforms.

Study of Subsonic Flow Over a TOW 2B Missile

The objective of this investigation is to study the subsonic flow over a missile. In this paper, a model of TOW 2B missile is studied. Two computational approaches are being explored, namely solutions based on the Reynolds-averaged compressible Navier-Stokes equations and solutions based on the inviscid flow (small disturbance theory). The simulations are performed at the Mach number of 0.6, 0.7, 0.8, 0.9 and 1.0 at four angles of attack of 2, 4, 6 and 8 degree. Results obtained from analytical simulation are compared with numerical data. It is found that lift and drag coefficients would go up by increasing of the angle of attack and the Mach number. Trend of changes of the results that obtained from the small disturbance theory is roughly as same as the numeric solution.

Enhanced Power Generation From Two-Winding Single-Phase SEIG Using LMDT-Based Decoupled Voltage and Frequency Control

This paper proposes a leaky minimal disturbance theory (LMDT)-based decoupled control of voltage and frequency for two-winding single-phase self-excited induction generators (SEIGs) for enhanced power generation and power quality improvement. Single-phase two-winding SEIGs are normally designed with 33% derated capacity in comparison to three-phase SEIGs of the same frame size. Using single-point operation performed by the proposed decoupled voltage and frequency controller (DVFC), the two-winding single-phase machine can generate enhanced power output, nearly 33% higher than its normal capacity. It is equal to the power generated by a three-phase machine with the same frame size. The DVFC consists of a voltage source converter (VSC) and a closed-loop controlled dump load. A single-phase VSC is used for harmonics and fundamental reactive power compensation for system voltage control and harmonics mitigation. The control of VSC is achieved using an LMDT-based control algorithm. The minimal disturbance theory-based control algorithm is used for potentially fast convergence and fast dynamic response, whereas the leakage factor is added for improving the steady-state performance of the system. The LMDT control-based VSC-battery energy storage system scheme is also implemented for the voltage and frequency control of a single-phase SEIG. Both schemes are implemented in real time using a digital signal processor.

Theoretical Study of a Diesel‐Filled Airtight Structure Unit Subjected to Shaped Charge Jet Impact

AbstractDiesel composite armor has high penetration resistance and can be used in tank vehicles to improve their protective capability and increase fuel oil storage. This study provides a theoretical calculation method to investigate the interaction between a shaped charge jet and a diesel‐filled airtight structure unit. Disturbance theory can predict the part of the jet that is disturbed by diesel fuel. The lumen radius for the container was varied to study its influence on the disturbance capability. A great lumen radius is found to cause lower maximum and minimum speeds of the disturbance velocity range of the jet, as well as a narrower disturbance velocity range. The reliability of the theoretical results was validated by experiments, and the experimental data show good agreement with the theoretical results.

Statistical characteristics of atmospheric phase fluctuations observed by using same-beam VLBI

When the signals from spacecrafts and radio sources transmits through the earths atmosphere and ionosphere, their phase occurs fluctuation, which has great influence on the measurement precision of the ground observing system such as VLBI. Using same beam VLBI data of 1 year which were got from two satellites (Rstar and Vstar) in Japanese lunar exploration project SELENE, we studied the Allan standard deviation and the structure function of correlation phase fluctuations of Rstar and Vstar, and differential correlation phase fluctuation between Rstar and Vstar on six baselines. We also obtained Allan standard deviation of phase fluctuations of Rstar and differential phase fluctuation between Rstar and Vstar at each station based on the 6 baseline data. In addition, we obtained the relationship model between differential phase fluctuations of Rstar and Vstar and its separation angle at each station. In the range of time interval 8 τ τ 0, which obeys Kolmogorov disturbance theory. The relationship model between the root mean square of differential phase fluctuations of Rstar and Vstar and its separation angle at each station is φ =1.967 θ +0.738 deg/deg, and that on six baselines is φ =2.759 θ +1.069 deg/deg.

Combined Effects of EDL and Boundary Slip on the Stability of Liquid-Liquid Viscosity-Stratified Flow in Microchannels

AbstractThe stability of pressure-driven liquid-liquid viscosity-stratified microchannel flow is investigated by considering the combined effects of electrical double layer (EDL) and boundary slip. The electrical streaming currents determined by the Streaming Electrical Current Balance (ECB) and the boundary slip are considered by Navier slip assumption. The stability of flow is studied by the small disturbance theory. Numerical results indicate that the effect of boundary slip on the flow stability is strongly depended on the EDL. The boundary slip stables the flow when EDL effect is weak and destabilizes the flow when EDL effect is strong. The effects of boundary slip and EDL on flow stability is also determined by viscosity ratio, the height of channel, interface position and conductivity ratio.

Ecological Analysis of Disturbance and Disturbance Intensity Estimates for Rainwater Harvesting

From an ecological perspective, the nature of rainwater harvesting with the characteristics of artificial disturbance is a manual disturbance. So it is very important to confirm the degree of ecological disturbance that occurs due to rainwater harvesting. Drawing from ecological disturbance theory, we can utilize both the distance method and dynamic curve method to estimate the level of ecological disturbance and degree of rainwater harvesting with a historical reference point value of the environment as a frame of reference, and with the 20 indicators such as surface runoff and evaluation index. Our examples show that the distance method and dynamic curve method are feasible for evaluating the ecological disturbance degree of rainwater harvesting. There are also research-scale effects in the study of ecological disturbance of rainwater harvesting that embody the comparability of different spatial and temporal ecological disturbance degrees. The comparability of ecological disturbance degrees of rainwater harvesting in an area at different scales or in different areas at the same scales is not strong, but it also generates some useful reference values. The ecological disturbance measurement in the same study area and at the same research-scale at different historical periods can be compared.

Comparative study on macrobenthic community structure with special reference to oligochaetes during drought and flooded phases in a Tropical Kole wetland, India.

Wetlands experience dynamic hydrofluxes which is a major determinant of biotic community structure. Benthic organisms form an integral part of aquatic environment and constitute an important link in the food web. The habitat loss and fragmentation caused by hydrological alterations in wetlands can affect the benthic fauna. This study analyzed the benthic community especially oligochaete species in a wetland during two different phases. Maranchery Kole wetland, a part of Vembanad Kole wetlands (Ramsar site) behaved as two systems within a short span of one year; as flooded phase when the system was a pure aquatic body and drought phase where the system was dry resembling a grass land with isolated water patches. Macrobenthic abundance in flooded and drought phases were (355±122 ind./m 2 ) and (166±60 ind./m 2 ) respectively. The decrease in habitable area along with its consequential effects resulted in a reduced numerical abundance of macrobenthos in the drought phase. Oligochaete abundance was significantly higher in flooded phase (ANOVA F 1, 53 =5.11, p 0.05). Species richness (Margalef’s index) and species diversity (Shannon Wiener index) was higher in drought phase or disturbed phase than flooded phase or undisturbed phase reflecting a glimpse of intermediate disturbance theory. No significant correlation emerged between the environmental variables and benthic abundance implying that the relationship with the measured environmental variables might be weaker or overridden by other unmeasured variables. Further the generalized environmental requirements in aquatic oligochaetes and chironomid larvae, the most abundant taxa in the wetland could be the reason for the lack of correlation.

Structure and floristic diversity of remnant semideciduous forest under varying levels of disturbance

The perturbation of Neotropical forests generates large disturbances in biological communities. The species that suffer least from the resulting habitat fragmentation are the pioneers, because they possess greater ability to inhabit disturbed environments. Therefore, it is expected that species diversity will be greater in areas subjected to intermediate disturbance, such as the opening of gaps, because a large number of pioneer species will develop and coexist with species of more advanced successional stages. This study aimed to compare two forest remnants that differed in size and disturbance intensity, in order to determine the effects of disturbances on species diversity and the size ratios of individual trees. This was accomplished with comparative analyses of diversity, richness and diameter ratios obtained for 10 plots at two semideciduous forest sites. We recorded a total of 85 species, of which 70 were in the private nature reserve Fazenda Santa Maria, 58 were in Iguacu National Park, and 43 were at both sites. Diversity was greater in the more disturbed remaining forest, because this area showed higher species richness, which is in accordance with some premises of the intermediate disturbance theory. There was also an increase in the number of pioneer individuals, and the less disturbed area showed individuals with larger diameters, which is likely attributable to the removal of large individuals from the more disturbed area during the anthropogenic process of forest modification.

A succession of theories: purging redundancy from disturbance theory.

The topics of succession and post-disturbance ecosystem recovery have a long and convoluted history. There is extensive redundancy within this body of theory, which has resulted in confusion, and the links among theories have not been adequately drawn. This review aims to distil the unique ideas from the array of theory related to ecosystem change in response to disturbance. This will help to reduce redundancy, and improve communication and understanding between researchers. We first outline the broad range of concepts that have developed over the past century to describe community change in response to disturbance. The body of work spans overlapping succession concepts presented by Clements in 1916, Egler in 1954, and Connell and Slatyer in 1977. Other theories describing community change include state and transition models, biological legacy theory, and the application of functional traits to predict responses to disturbance. Second, we identify areas of overlap of these theories, in addition to highlighting the conceptual and taxonomic limitations of each. In aligning each of these theories with one another, the limited scope and relative inflexibility of some theories becomes apparent, and redundancy becomes explicit. We identify a set of unique concepts to describe the range of mechanisms driving ecosystem responses to disturbance. We present a schematic model of our proposed synthesis which brings together the range of unique mechanisms that were identified in our review. The model describes five main mechanisms of transition away from a post-disturbance community: (i) pulse events with rapid state shifts; (ii) stochastic community drift; (iii) facilitation; (iv) competition; and (v) the influence of the initial composition of a post-disturbance community. In addition, stabilising processes such as biological legacies, inhibition or continuing disturbance may prevent a transition between community types. Integrating these six mechanisms with the functional trait approach is likely to improve the predictive capacity of disturbance theory. Finally, we complement our discussion of theory with a case study which emphasises that many post-disturbance theories apply simultaneously to the same ecosystem. Using the well-studied mountain ash (Eucalyptus regnans) forests of south-eastern Australia, we illustrate phenomena that align with six of the theories described in our model of rationalised disturbance theory. We encourage further work to improve our schematic model, increase coverage of disturbance-related theory, and to show how the model may link to, or integrate with, other domains of ecological theory.

Experimental investigation on SPS casing treatment with bias flow

Generally, casing treatment (CT) is a passivity method to enhance the stall margin of fan/compressor. A novel casing treatment based on the small disturbance theory and vortex and wave interaction suggestion is a method combining passive control and active control, which has been proved effective at enhancing the stall margin of fan/compressor in experiment. In order to investigate the mechanism of this kind of casing treatment, an experimental investigation of a stall precursor-suppressed (SPS) casing treatment with air suction or blowing air is conducted in the present paper. The SPS casing treatment is designed to suppressing stall precursors to realize stall margin enhancement in turbomachinery. The experimental results show that the casing treatment with blowing air of small quantity can improve the stall margin by about 8% with about 1% efficiency loss. By contrast, the SPS casing treatment with micro-bias flow does not improve the stall margin much more than that without bias flow, even worse. Meanwhile, the present investigation has also attempted to reveal the mechanism of stall margin improvement with the casing treatment. It is found that the stall margin improvements vary with the modification of the unsteady shedding flow and the unsteady wall boundary impedance. The experimental results agree fairly well with the theoretical prediction using a flow stability model of rotating stall.

Modeling and Approximation of STOL Aircraft Longitudinal Aerodynamic Characteristics

Flight dynamics deals principally with the natural response of the aircraft to longitudinal perturbations that typically consist of two underdamped oscillatory modes having rather different time scales. One of the modes has a relatively short period and is usually quite heavily damped. This is called the short period mode. The other mode has a much longer period and is rather lightly damped. This is called the phugoid mode. The required degree of dynamic stability is specified by the time it takes the motion to damp to half of its initial amplitude. The dynamic characteristics of an airplane is important in assessing its handling or flying qualities and for designing autopilots. This paper investigates the dynamic characteristics of short take off and landing (STOL) airplanes employing root locus technique and state space approach. The nonlinear differential equation of motion of an airplane developed from Newton’s second law of motion was linearized using the small disturbance theory. Different phugoid approximations for longitudinal modes were developed and compared with the exact solution formulated using statistical software. Further research work about active control technology to improve aerodynamic efficiency which results in potential fuel savings should be carried out.