Consulting Engineer cheat sheet

Earned Value: CV = EV − AC; SV = EV − PV; CPI = EV/AC; SPI = EV/PV. Negative CV or SV means cost overrun or schedule slippage against the baseline.

Estimate at Completion: EAC = BAC/CPI when current cost efficiency is expected to persist; EAC = AC + (BAC − EV) when remaining work is expected to proceed at the planned rate.

To-Complete Performance Index: TCPI = (BAC − EV)/(BAC − AC) for budget-constrained work; a TCPI above 1.0 means the team must outperform the plan to finish within budget.

Critical path is the longest duration path through the network; it has zero total float. Total float = LS − ES = LF − EF. Free float is delay possible without moving any successor's early start.

Program management coordinates related projects for consolidated benefit; a project manager optimizes one project's triple constraint, while a program manager arbitrates shared resources and inter-project dependencies.

Scope change control: any change to the approved scope baseline passes through integrated change control, producing a change request, impact assessment across scope, schedule, cost, and risk, then approval or rejection.

RACI matrix rules: exactly one Accountable per activity; Responsible does the work; Consulted is two-way input; Informed is one-way notification. Multiple Accountable owners create ambiguity.

Risk response selection: avoid eliminates the threat, mitigate reduces probability or impact, transfer shifts financial consequence (insurance, fixed-price contract), accept retains exposure with a contingency reserve.

Schedule compression: crashing adds resources to critical-path activities at added cost; fast-tracking overlaps sequential activities and adds rework risk. Neither shortens non-critical paths.

Net Present Value: NPV = Σ CFt/(1+r)^t − initial investment. Accept independent projects with NPV > 0; among mutually exclusive projects, select the highest NPV.

Internal Rate of Return is the discount rate making NPV = 0. IRR can mislead for non-conventional cash flows or when project scale differs; NPV is the primary decision rule.

Payback period ignores cash flows after the cutoff and the time value of money; discounted payback corrects for discounting but still ignores post-payback value.

Profitability Index = PV of future cash flows / initial investment. PI > 1.0 is acceptable; it ranks projects under capital rationing but can favor small projects.

Weighted Average Cost of Capital: WACC = (E/V)·Re + (D/V)·Rd·(1 − tax rate). It is the hurdle rate for projects of average risk; riskier projects warrant a higher discount rate.

Break-even quantity = Fixed costs / (Unit price − Unit variable cost). Operating leverage rises with fixed-cost share, amplifying the sensitivity of profit to volume changes.

Sunk costs are excluded from incremental analysis; opportunity costs and incremental cash flows, including working capital changes and tax effects, are included.

Depreciation is non-cash but shields taxable income. Under straight-line, annual depreciation = (Cost − Salvage)/Useful life; accelerated methods raise early-year tax shields.

Unit consistency is mandatory before any calculation: convert to a coherent system (SI or US customary) and carry units through every step to catch dimensional errors.

Significant figures: multiplication and division retain the least number of significant figures in the inputs; addition and subtraction retain the least number of decimal places.

Root-sum-square combination applies to independent random uncertainties: u_total = √(u1² + u2² + …). Systematic or correlated errors are added linearly, not in quadrature.

Design factor (safety factor) = failure strength / allowable stress. A higher design factor covers greater uncertainty in loads, material properties, and consequences of failure.

First law for a steady-flow open system: Q − W = ṁ[(h2 − h1) + (V2² − V1²)/2 + g(z2 − z1)]. Neglect kinetic and potential terms only when justified by magnitude.

Beam deflection scales with span to the fourth power for a uniformly loaded simply supported beam (δ = 5wL⁴/384EI); doubling span increases deflection about sixteenfold.

Sensitivity analysis identifies which input most affects the output; a tornado diagram ranks variables by swing. Monte Carlo simulation propagates input distributions to an output distribution.

Model validation asks whether the model represents the real system for its intended use; verification asks whether the model was implemented correctly. They are distinct checks.

Standard of care for professional services is the degree of care and skill ordinarily exercised by members of the profession under similar circumstances, not a guarantee of perfect results.

Negligence requires four elements: a duty of care owed, a breach of that duty, causation (actual and proximate), and damages. Missing any element defeats the claim.

A fixed-price contract shifts cost-overrun risk to the seller; a cost-reimbursable contract shifts it to the buyer, usually with a fee and a cost ceiling.

Contract formation requires offer, acceptance, consideration, and mutual assent; a counteroffer operates as a rejection of the original offer.

Conflict of interest rules require disclosure and, where the conflict is material, written consent or withdrawal. Undisclosed conflicts undermine the independence on which professional advice relies.

Public safety paramountcy: when a client instruction would create an unacceptable risk to public health or safety, the engineer must refuse, document the objection, and escalate as required.

Records retention and privilege: mark legal-hold documents, avoid destroying records once litigation is reasonably anticipated, and route privileged communications only to counsel.

Licensure is jurisdiction-specific; practicing or sealing work outside one's licensed scope is a legal violation even when technically competent.

Stakeholder power/interest grid: high power–high interest are manage closely; high power–low interest are keep satisfied; low power–high interest are keep informed; low–low are monitor.

Requirements elicitation separates stated wants from underlying needs; confirm each requirement in writing and trace it to a design element or deliverable.

Communication plan defines audience, message, channel, frequency, and owner. Escalation paths and decision rights should be agreed before disputes arise.

Expectation management: document assumptions and exclusions in the proposal and contract; unstated assumptions become disputed scope later.

Active listening techniques-paraphrasing, summarizing, and open questions-reduce misunderstanding; confirm verbal agreements with written minutes distributed promptly.

Change in client priorities is handled through the change control process, not informal side agreements; quantify schedule, cost, and quality impact before acceptance.

Confidentiality: client information is used only for the engagement, shared on a need-to-know basis, and protected after the engagement ends.

Handling dissatisfaction: acknowledge the concern, gather facts, propose a remedy with a timeline, and record the resolution. Escalation to senior management should be planned, not reactive.

Quality assurance is process-focused and preventive; quality control is product-focused and detective (inspection, testing). QA aims to prevent defects that QC would otherwise find.

Risk score = Probability × Impact. Prioritize by score; reserve contingency for known risks and management reserve for unknown-unknowns.

Hierarchy of controls, most to least effective: elimination, substitution, engineering controls, administrative controls, personal protective equipment.

ALARP principle: risks are reduced so far as is reasonably practicable; residual risk must be documented and accepted by the accountable authority.

PDCA (Plan-Do-Check-Act) drives continuous improvement; root-cause tools include the 5 Whys and fishbone (Ishikawa) diagrams.

Risk register fields: ID, description, cause, trigger, probability, impact, score, owner, response strategy, residual risk, and status.

Incident investigation seeks root causes, not blame; corrective actions must be tracked to closure and verified for effectiveness.

Quality cost categories: prevention and appraisal costs are conformance costs; internal and external failure costs are nonconformance costs, with external failure typically the most expensive.